The science behind intermittent fasting
August 20, 2012 3:07 AM   Subscribe

The benefits of fasting have been covered before on Metafilter, but a new BBC documentary (discussed by the presenter Dr Michael Mosley in the Telegraph here) looking at the science behind fasting seems to show that the evidence supporting fasting’s general health benefits beyond weight loss are growing.
posted by MighstAllCruckingFighty (97 comments total) 138 users marked this as a favorite

 
Instead I opted for a less dramatic variant: the 5:2 diet. With this regimen you eat what you want five days a week, then twice a week you restrict yourself to just 600 calories.
posted by pracowity at 3:16 AM on August 20, 2012 [3 favorites]


In the documentary he says that the 5:2 diet has most of the benefits of fasting, but that it is very much a compromise between what seems to be optimal from a health standpoint (i.e. fasting for extended periods) and living the reality of everyday life.
posted by MighstAllCruckingFighty at 3:26 AM on August 20, 2012


I'm deeply suspicious about another fad diet presented as a panacea to good health. Fasting may work, so might eating healthy most of the time. I enjoyed another Mosley doco I watched, but more because it was investigating the cost that bad choices have on the body.

This.... I'm not so sure. What was his diet and fitness like before?
posted by smoke at 3:40 AM on August 20, 2012


In the documentary there a lot of time is spent on before and after (blood results, etc.).

I should point out that it said this diet is dangerous for kids, pregnant women, those suffering certain medical conditions and those who are underweight.
posted by MighstAllCruckingFighty at 3:44 AM on August 20, 2012


Just to contextualize this a little for non-UK people: Michael Mosley trained as a doctor but then joined the BBC to produce science documentaries, and in recent years has emerged as an impressive host of medical documentaries, such as an excellent series on the history of surgery and others on medical mavericks, the brain, exercise, aging and weight loss. They're all well worth watching. Mosley is very much on the non-woo end of the spectrum, so when he says at the end of this latest Horizon documentary that it has affected him like no other, it certainly gets your attention.
posted by rory at 3:47 AM on August 20, 2012 [28 favorites]


Smoke, he talks about his levels of fitness in the documentary, but you could also track down his Horizon docs on exercise and the gut for more context. Basically, he's just a typical middle-aged Western male, tending to being overweight, too much intra-abdominal fat, that sort of thing.
posted by rory at 3:53 AM on August 20, 2012


Horizon: The Truth About Exercise

Guts: The Strange and Mysterious World of the Human Stomach
posted by rory at 3:56 AM on August 20, 2012 [5 favorites]


This is interesting but it's going to take many years of before this has been properly researched so that scientists can establish that fasting is better than a normal diet and regular exercise.
posted by Foci for Analysis at 3:59 AM on August 20, 2012 [1 favorite]


I do like the idea of a diet that encourages people to just eat less, if only for two days a week, rather than promoting the latest combination of food that is supposedly just right for the human body.
posted by pracowity at 4:05 AM on August 20, 2012 [5 favorites]


None of this is surprising. Most of human history has been spent fasting which is what you do between meals. Surely our human ancestors, living off the land, experienced frequent periods of time when food was scarce and the body has over time adapted to this.
posted by three blind mice at 4:11 AM on August 20, 2012 [4 favorites]


A perfect diet and regular exercise are often just that little bit out of reach for many people for all sorts of reasons, some practical ("I don't have time for much exercise"), some psychological ("I love good home cooking, and leafy vegetables bore me"). Having a range of very different approaches to improving general health, even if many of them are non-optimal, can only really be a good thing. The idea (that seems quite common in these discussions) that we all need to be doing precisely the same things to improve our health outcomes seems to me to be unnecessarily prescriptivist.
posted by pipeski at 4:12 AM on August 20, 2012 [19 favorites]


What got me about this documentary wasn't the weight-loss aspect, but that fasting appears to encourage the body to repair damaged cells, potentially decreasing the risks of cancer, diabetes and even Alzheimer's. That's far more compelling than just another diet plan.
posted by rory at 4:14 AM on August 20, 2012 [15 favorites]


Funny, this post came the day after Muslims celebrate the end of Ramadan, the month when Muslim people fast during the daylight hours...
posted by Katjusa Roquette at 4:14 AM on August 20, 2012 [7 favorites]


I would like this to be true, but without long term trials I can't accept anything anyone says about nutrition.

There was been too many fads for me to have any trust.

All I do now is as Michael Pollan says, "Eat food. Not too much. Mostly plants".
posted by KaizenSoze at 4:29 AM on August 20, 2012 [4 favorites]


Given how long it's taken Taubes to disprove the reigning theories of obesity and fat, there's no way there's enough of the right kind of evidence to prove that fasting or even 5:2 is good for you, or why and compared to what.

Making a public push like this is a bad idea, precisely because it makes me, an ordinary bloke think: hmmm, maybe I'll ditch my current diet and try that.
posted by anotherpanacea at 4:42 AM on August 20, 2012 [1 favorite]



Given how long it's taken Taubes to disprove the reigning theories of obesity and fat, there's no way there's enough of the right kind of evidence to prove that fasting or even 5:2 is good for you, or why and compared to what.


Taubes proved that the low fat theory was based on bad science, which I thank him for. Then he stuck up his own theory with even less science.

People lose weight on both low fat and low carb diets, both have poor sustainability over the long term.
posted by KaizenSoze at 4:45 AM on August 20, 2012 [12 favorites]


I am also skeptical about yet another diet, but maybe because I hit the bit about "not too much protien" when for years I've been hearing that people should eat more protien.

and that just leaves me thinking - the science bits are interesting, but I don't care to hear anything more about how I should eat, unless it's "add more hot sauce". I don't make much, so I probably won't be able to afford to retire for long anyways -- and I'd be happier living 55 years enjoying food than 85 years worried about what I eat all the time (as the "healthy" people in my family do). I'll try to keep up the moderate exercise, because I don't want to become prematurely disabled.

but I've learned from movies that living forever is a curse, and from my own family that living long after your friends are gone isn't much fun either.
posted by jb at 4:54 AM on August 20, 2012 [4 favorites]


Anecdata: I've lost over 100 lbs in 250 days since I went to 16/8 Intermittent Fasting to drive a net-caloric balance. It's been working really well. It was that thread in december about glucose intolerance where everyone chimed up that they didn't like to eat breakfast which gave me the comfort level to go ahead. Combined with a homebrewed net-caloric-balance monitor ( Walker 1991 ) it's been a sustainable, low stress, no-menu-planning way of meeting my goals.
posted by mikelieman at 5:03 AM on August 20, 2012 [15 favorites]


I often worry that these fads basically work for the people they work for. People who don't feel much discomfort from fasting (which is probably genetic) will find fasting a viable option, and then complain that the rest of us are slobs. My wife, if she's put on a couple of pounds, will just announce, "I'm not going to eat today", and seems to experience no problems. If I miss lunch, I'm exhausted and irritable by the evening, and if I don't eat in the evening, I can't sleep for the hunger pangs.
posted by raygirvan at 5:06 AM on August 20, 2012 [3 favorites]


Although I agree completely with pipeski and raygirvan that a range of approaches is better than saying you must do this one thing... I've actually started doing the 5:2 method after watching the BBC program a few weeks ago.

For me it makes sense. It doesn't seem like a big hardship to eat a bit less twice a week, and I thought about how every culture seems to have some fasting system built into it, so it's probably not harmful. I've lost a few pounds and otherwise it seems much less disruptive than the average fad diet.
posted by maggiemaggie at 5:09 AM on August 20, 2012 [1 favorite]


I watched this Horizon when it first went out on BBC 2, and I thought the truly astonishing part was Joe Cordell's experience with the Calorie-Restricted Optimum Nutrition diet he follows. It runs from 10:00 to 18:17 on the YouTube link.

Cordell's followed this diet for ten years now, which as far as I can see involves eating mountains of fruit and veg but very little else. He consumes about 1,900 calories a day, and he's in his fifties.

Mosley, who I gather is about the same age, took Cordell for a series of medical tests at Washington University, where a professor there analysed both men's results. He concluded that Cordell's risk of heart attack or stroke in the future was practically zero, while Mosley's was all but certain. What's more, he said that if Mosley followed Cordell's regime for just one year, he could reduce his own risk factors to the same near-zero level.

If it weren't for the fact that two serious scientists were saying this, I'd be quick to dismiss it as just another bullshit diet fad designed to part gullible fatties from their cash. As the story was presented here, though, I have to admit it looked pretty impressive.
posted by Paul Slade at 5:16 AM on August 20, 2012 [8 favorites]


I'm actually following this 5:2 fasting regime at the moment, having started when the documentary aired. I share the skepticism here, but the documentary was convincing enough for me to try it.

A huge part of why I wanted to try this particular diet is that it looks sustainable. A couple of years ago I did manage to lose a hell of a lot of weight, between 10-15 kilos (and still ended up > 110 kilos), which was done through a combination of intensive workouts (3-4 times per week) and sustained dieting, but mainly through having the incentive of needing to slim down quickly enough to convince the surgeons I could undergo a kidney transplant operation. Oddly enough, once that was done the urge to continue this regime disappeared.

What I need therefore is something that I can keep up longtime and does make me lose weight gradually, which this looks to be doing. It's way to early to tell of course, but I have high hopes.
posted by MartinWisse at 5:38 AM on August 20, 2012 [5 favorites]


Taubes proved that the low fat theory was based on bad science, which I thank him for. Then he stuck up his own theory with even less science.

Yeah, well, he had to stick with it to get the establishment to pay attention. And now there is good science to back him up. (This study is a game changer, methodologically, but even it has a relatively low n and lots of ceteris paribus issues.)
posted by anotherpanacea at 5:46 AM on August 20, 2012


Unless you choose a diet that you can sustain for the rest of your life, going on one of these sorts of diets dooms you to ultimate weight regain. And I'm deeply suspicious of any diet that says "eat what you want" as part of the plan. If you're in the position to lose weight, then eating what you wanted is what got you in that position. 2 days of fasting is never going to counteract 5 days of double-cheeseburgers, twinkies, pizza and beer.
posted by crunchland at 5:51 AM on August 20, 2012 [4 favorites]


My guess is that this will join all the other fads that purport to make everyone healthy but over time fall by the wayside. I can't see it doing any harm for most people (we certainly didn't evolve with fully stocked refrigerators and convenience stores on every block) but I doubt it will have the huge impact this initial description is promising.

As a trick to lower your overall caloric consumption, this will work great, just like cutting out an entire class of food (no simple carbs, say) does, and that probably has more impact than whether those calories are spread evenly over the week or not.
posted by Forktine at 5:54 AM on August 20, 2012


See you all in 18 months when oh no! Fasting now causes cancer!
posted by GallonOfAlan at 5:59 AM on August 20, 2012 [10 favorites]



Yeah, well, he had to stick with it to get the establishment to pay attention. And now there is good science to back him up. (This study is a game changer, methodologically, but even it has a relatively low n and lots of ceteris paribus issues.)


Only a short term study, each diet was tried for four weeks. The problem is the long term maintenance.

Maybe in another ten years, we'll have long term studies.
posted by KaizenSoze at 6:13 AM on August 20, 2012


2 days of fasting is never going to counteract 5 days of double-cheeseburgers, twinkies, pizza and beer.

They address this in the documentary. It seems that perhaps somewhat counterintuitively people have a lower desire to gorge on crap on their feast days. This diet is also not specifically about weight loss, although that is clearly a benefit. The purported main advantages of this diet is that it reduces your risk of cancer, Alzheimer's, strokes, etc. It slows the rate that you age down.
posted by MighstAllCruckingFighty at 6:15 AM on August 20, 2012


Fasting's hardly new, or a fad. Much of the research that I'm familiar with, about exercising in a fasted state and so on, comes from research done with people fasting for Ramadan.
posted by gingerbeer at 6:29 AM on August 20, 2012 [2 favorites]


There was a good article about this in Harper's a few months ago: "Starve Your Way To Health" by Steve Hendricks. (Not on-line except behind a Harper's registration-wall.) The article focussed on the health benefits of short fasts, which seem considerable and well-documented. (It's not very effective as a permanent weight-loss diet unless you are very disciplined after you go off the fast, in which case you might as well just start off disciplined in your eating habits and lose weight that way.)
posted by Harvey Kilobit at 6:32 AM on August 20, 2012


Funny, this post came the day after Muslims celebrate the end of Ramadan, the month when Muslim people fast during the daylight hours...

... and many still gain weight, because they eat lots when the sun go down.

From the NPR link: "If you're not eating all day and you can think of all the yummy things that you can have at night and, you know, the sun goes down and you can have anything you want, it is easy for some people to overeat, especially if they're not concerned about their health."

This could also be a problem with intermittent fasting. It seems that every single diet plan leaves some "loopholes". Low carb = unlimited amounts of bacon and vodka, right?
posted by iviken at 6:33 AM on August 20, 2012 [1 favorite]


See you all in 18 months when oh no! Fasting now causes cancer! posted by GallonOfAlan at 6:59 AM on August 20 [+] [!]

There's been many a Surgeon (Gastric) that has told me exactly that, after seeing that I had been fasting for years and losing about 50 lbs.
(disclosure: I'm an Ortho surgeon myself, and under no interpretation this should be considered medical advice/bet insurance/proof/scientific data/evangelization or support of this theory)
posted by youhavetoreadthistwice at 6:35 AM on August 20, 2012


Fast Mondays and Thursdays.
posted by Burhanistan at 6:36 AM on August 20, 2012


Fasting is not a panacea it is a tool. It goes along with taking care with what you put into your body, exercising, and coping with everyday stress. Judging by the tubs of American lard I passed on my way to work today we could all benefit from skipping a few meals.

I have done a 21 hour once a week fast for several months at a time. This, coupled with restricting grain consumption, has provided me additional energy, less inflammation (tendinitis) and some weight loss (though that's not a primary concern for me).
posted by incandissonance at 6:42 AM on August 20, 2012 [3 favorites]


I have done a 21 hour once a week fast for several months at a time. This, coupled with restricting grain consumption, has provided me additional energy, less inflammation (tendinitis) and some weight loss (though that's not a primary concern for me).

Yeah, and you're one data point. Don't make the mistake of assuming that what worked for you works for everyone, because I know people who have no health problems and live on a pizza and beer. The human body is complex and there are diverse processes that affect each of us differently.

The "tubs of American lard" comment you made suggests that now that you've solved your food issues, perhaps you could put the same effort into developing empathy and a better understanding for the socio-economic and genetic causes of obesity that are more impacting than personal decision-making.
posted by Rodrigo Lamaitre at 6:47 AM on August 20, 2012 [25 favorites]


As a brilliant friend of mine said, "the plural of anecdote is not data". However, this idea of fasting occasionally seems like a really good way of cutting total calorie consumption, and if the results of Mosley's four day fast are anything like typical, then there's probably good reason to put some stock in the idea of fasting. Once when I was depressed I didn't eat for three days, and was none the worse for it, and actually ended up finally working the energy to leave the house and get groceries and cook and clean afterwards (although that is all just fluff). I think I'll try cutting my intake two days a week. Can't see any harm.
posted by cthuljew at 6:57 AM on August 20, 2012


this is interesting. i think i kinda do this already sometimes. there are some days where i am just not hungry, even tho i haven't really eaten anything, or i don't feel like eating anything and it doesn't seem to have anything to do with how much exercise or sleep etc i've been getting/not getting. if i don't eat on those days, i feel just fine. if i force myself to eat, even just salad or soup, something light, i end up feeling like i've stuffed myself.

i've noticed my cravings are down when i stick to mostly paleo. but i'm still mystified when i can eat two eggs and four pieces of bacon and be absolutely ravenous less than two hours later. (like today. seriously body, wtf?)

the only difference for me is that if i were to eat toast or hashbrowns with that eggs and bacon, i wouldn't just be hungry i 'd also be sleepy. guess that's the blood sugar crash. (ps my cholesterol etc is just fine. had blood work not too long ago.)

i'll have to give this a watch later when i'm home. i'm glad to hear it's science and not woo.
posted by sio42 at 7:08 AM on August 20, 2012


I often worry that these fads basically work for the people they work for. People who don't feel much discomfort from fasting (which is probably genetic) will find fasting a viable option, and then complain that the rest of us are slobs.

In the past few years I've seen changes in the way that diet gets discussed in public forums, especially Metafilter, in a good way. One of those changes is the growing realization that weight loss is highly individual. Another is the recognition (spurred by Taubes and others) that it's not just calorie reduction, except when it is.
posted by mecran01 at 7:11 AM on August 20, 2012 [4 favorites]


Meh, fasting gives me epic migraines. UNFAIR.
posted by elizardbits at 7:56 AM on August 20, 2012 [1 favorite]


As a brilliant friend of mine said, "the plural of anecdote is not data".

I'll bet your brilliant friend didn't tell you that the *anagram* of anecdote is "need taco."
posted by weston at 8:25 AM on August 20, 2012 [48 favorites]


Does nobody else become an angry monster without enough food? 600 calories a day for two days out of the week would destroy my marriage.
posted by something something at 8:29 AM on August 20, 2012 [12 favorites]


> Does nobody else become an angry monster without enough food?

Maybe the first time...but bodies adjust. Besides, it's an interesting psychological study one can do on one's self. Why is it that food has such a powerful influence on mood?
posted by Burhanistan at 8:35 AM on August 20, 2012 [1 favorite]


Fasting is great when you've been eating badly (because of stress or whatever). For me it's like a system reset, the urge to eat greasy sugary crap just goes away.
posted by subdee at 8:36 AM on August 20, 2012 [3 favorites]


I suspect that regular fasting also has the psychological side-effect of helping develop self-awareness, willpower and discipline that can be applied on non-fast days.
posted by mr.ersatz at 8:50 AM on August 20, 2012 [8 favorites]


Meh, fasting gives me epic migraines. UNFAIR.

Complete fasting has similar effects on me... it's a pretty good way to wreck me for large portions of the day.

Cutting back to limited servings means less food joy, but doesn't seem to have the same problems.
posted by weston at 8:57 AM on August 20, 2012


I had the fortunate experience of hearing about the benefits of calorie restriction (not fasting, per se, but I skip meals pretty often) at a very early age (10? 12?) and have been practicing a (mostly casual) version of it ever since...the goal being longevity. Mostly, I just don't keep a ton of food around the house, never feel like eating in the morning, and try to eat more healthy green stuff, and mostly all of that raw/fresh. (well, I try to try, I DO have a sweet tooth) And I don't jump on every fad...those notions about 'eating nothing but protein' or 'lets do a sugar-water fast for a month!' just sound like insanity to me.
By the charts I am somewhat underweight (125 lbs at 5'8") but, those charts are based on the general population (and we know how fat They are) and change about as often as food fads, so I don't worry about it too much...my blood pressure is nice and low, my cholesterol nonexistant, and my general health is really good.
Oh, and most people who meet me think I am in my early-to-mid 20's (I get carded for everything, everywhere, every time)...I am 40.
posted by sexyrobot at 9:02 AM on August 20, 2012 [2 favorites]


Only a short term study, each diet was tried for four weeks. The problem is the long term maintenance.

Maybe in another ten years, we'll have long term studies.


Maybe you're aware of these and are looking for even longer-term studies, but studies of low-carbohydrate diets that last one year or two years demonstrate exactly what you said; that (quoting the 2-year study) "Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize."

The JAMA study by Dr. Ludwig's group linked above was not only short-term, conducted on a small sample, and produced highly-variable results, but it was also a study on maintenance of a reduced bodyweight, not weight loss. All subjects in the study reduced their weight with the same standard diet, which included carbs. It's been demonstrated many times that there is no metabolic advantage inherent in a low-carbohydrate diet. The carbohydrate/insulin hypothesis of obesity, popularized in part by Gary Taubes, is not taken seriously in the field of obesity research.
posted by ludwig_van at 9:04 AM on August 20, 2012 [2 favorites]


This post comes at a perfect time, I've been trying intermittent fasting (fasting every other day) for the past week and a half. It is very interesting. You would think you would eat more on your eating day, but you really don't. I think it is because my stomach must be shrinking on the fasting days. I've lost weight, I feel great, and it seems like something I could sustain for as long as I need to. I'm seeing some pretty dramatic results already, and after a few weeks I can go from fasting every other day to once or twice a week to once a month if I so desire. You also appreciate food more, you remember on your fasting day what you ate the day before, and look forward to eating whatever you would like the next day. I never drank tea before, but now on my fasting days I have a hot green tea. So I have tea 2-3 times a day where normally I would have a meal at that time. It keeps the ritual of a meal, which is psychologically comforting. I would highly recommend it.
posted by banished at 9:07 AM on August 20, 2012 [6 favorites]


Autophagy: Why you should eat yourself and a bunch of wiki-reading & googling convinced me there's a very strong case to be made that various forms of caloric restriction (overall & temporary) can be extremely beneficial to human health. I don't fast on any set schedule, but the knowledge that it's healthy allows me to go on spontaneous/accidental fasts (e.g. "I forgot breakfast/lunch ... I'll do a mini-fast, eat a tiny dinner and then have a huge meal tomorrow") and not feel like I have some eating disorder. The idea that people should eat meals on generally fixed schedule seems increasingly bizarre

Anecdatally, I've found fasting useful in keeping my weight where I want it (about 60 lbs of fat below where I've been, a couple times), and it's certainly useful for reflecting on the body and mind's wants and needs. One thing I often think is we do have a real need for food, but then use that as an excuse for recreational eating. i.e. often times a small portion of the exact thing I crave is enough to carry on fasting another half-day, where I'd normally eat 4x that amount just because om nom nom
posted by crayz at 9:12 AM on August 20, 2012 [2 favorites]


Does nobody else become an angry monster without enough food?

Fortunately not. Today for example I bought two sandwiches on the way home and that's all, apart from some fresh fruit and/or raw carrots to munch on later. The latter gives you that satisfying feeling of really nomming down on something without the filler. I do it on workdays because it's easier to avoid food and hunger signals when at work, as long as you stay away from the canteen.
posted by MartinWisse at 9:27 AM on August 20, 2012


Does nobody else become an angry monster without enough food?

I think that's one of the aspects which makes 16/8 fasting sustainable. I eat a normal lunch at noon, since I eat a normal lunch, I'm resistant to snacking until dinner. At 6 or 7, I eat a normal dinner, which helps me resist snacking until 8pm/bedtime. Lather, Rinse, Repeat. And since I have two meals that I'm dividing up my calories among, there's pretty much no need for menu planning, calorie counting, etc.
posted by mikelieman at 9:43 AM on August 20, 2012


Sleeping normally for five days a week and then not sleeping for two was pretty much how I lived out my 20s. Why not food? Although come to think of it I didn't eat much for those two days either.
posted by Blue Meanie at 10:07 AM on August 20, 2012 [1 favorite]


It's been demonstrated many times that there is no metabolic advantage inherent in a low-carbohydrate diet.

Could you give us a study showing that? The JAMA study suggests that resting energy expenditure is higher on a low- carbohydrate diet, and even though it's a small, short terms study following calorie restriction, it seems like we need a study that actually measures resting energy expenditure before we can say there's no metabolic benefit.

It's a different thing to say that the particular insulin hypothesis has been disproven: the mechanism might not be right, but the data suggests that something is happening.
posted by anotherpanacea at 10:12 AM on August 20, 2012 [1 favorite]


Here is a link to the Harper's article. Starving Your Way to Vigor: The Benefits of an Empty Stomach. As someone said above, it is a pay access only, but if you are a Harper's subscriber who somehow missed the cover story in March, it's worth reading. I want to believe this idea. But found myself just as skeptical after reading this article (and watching the documentary) as when I first heard about it. As a father with a 3 and 1 year old, sleep is vital and food helps keep my energy up. Maybe when the kids are grown.
posted by dogbusonline at 10:21 AM on August 20, 2012 [1 favorite]


I'm looking forward to trying this out. I know from experience that 600 calorie days are doable - something like soup for lunch, chicken and leafy greens for dinner more than fills me up. I just never had the insight to take it easy on myself and do this for 2 days a week instead of 5 or 6. Feeling like this is effective and sustainable in the long term.
posted by naju at 10:23 AM on August 20, 2012


Lately my relationship with food has gotten rather... angry. The 5:2 fasting plan sounds really interesting--it sounds like it could take some of the worrying out of my meals.

If this was in the documentary, I missed it: is the recommendation to space out those two days of fasting?
And I realize that more research needs to be done, but has anyone else been writing/talking about the 5:2 fasting? I see there's an ebook called "Eat Stop Eat", but it looks a bit dodgy. Anyone know anything about that?
posted by Baethan at 10:32 AM on August 20, 2012


If this was in the documentary, I missed it: is the recommendation to space out those two days of fasting?

Yes. The fast days should not be concurrent. You can have the 600 calories (500 for women) in one go, or snack throughout the day if you prefer.
posted by MighstAllCruckingFighty at 10:35 AM on August 20, 2012


For me, low carb eating substantially changed my hunger responses, which is what made IF feasible for me. I'm not sure I could have managed IF if I weren't already eating low carb. As it is, I do it 2-4 times a month without too much trouble. Of course, I've already fallen down the low carb/Taubes rabbithole.

I'm a fan of the Mark's Daily Apple blog and his multiple posts on the topic.
posted by gingerbeer at 10:42 AM on August 20, 2012 [1 favorite]


Could you give us a study showing that?

Metabolic ward studies:

Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets
Mean (±SE) weight losses (6.3 ± 0.6 and 7.2 ± 0.8 kg in KLC and NLC dieters, respectively; P = 0.324) and fat losses (3.4 and 5.5 kg in KLC and NLC dieters, respectively; P = 0.111) did not differ significantly by group after 6 wk.
Similar weight loss with low- or high-carbohydrate diets.
The goal of this study was to evaluate the effect of diets that were equally low in energy but widely different in relative amounts of fat and carbohydrate on body weight during a 6-wk period of hospitalization. Consequently, 43 adult, obese persons were randomly assigned to receive diets containing 4.2 MJ/d (1000 kcal/d) composed of either 32% protein, 15% carbohydrate, and 53% fat, or 29% protein, 45% carbohydrate, and 26% fat. There was no significant difference in the amount of weight loss in response to diets containing either 15% (8.9 +/- 0.6 kg) or 45% (7.5 +/- 0.5 kg) carbohydrate.
Effect of diet composition on metabolic adaptations to hypocaloric nutrition: comparison of high carbohydrate and high fat isocaloric diets.
The study, performed on a metabolic ward, compared the response of these men to two cholesterol-free liquid formula diets of differing composition (10 kcal/kg per day, 70% carbohydrate, 20% protein, 10% fat versus 70% fat, 20% protein, 10% carbohydrate) but identical in calories. These were administered for 14 days in a random order and each diet was preceded by a 7-day control weight maintenance diet (30 kcal/kg per day, 40% carbohydrate, 20% protein, 40% fat). The low calorie diets were well tolerated by the men and effected similar losses of nonaqueous body weight.
Diet composition and energy balance in humans.
Inpatient metabolic studies of human subjects were performed to obtain data on important nutritional issues. It was shown that wide variations in the ratio of carbohydrate to fat do not alter total 24-h energy need.
Reviews:

Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss?
A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restriction of carbohydrates.
Efficacy and safety of low-carbohydrate diets: a systematic review.
Among obese patients, weight loss was associated with longer diet duration (P =.002), restriction of calorie intake (P =.03), but not with reduced carbohydrate content (P =.90).
Energetics of obesity and weight control: does diet composition matter?
However, a review of studies in which 24-hour energy expenditure was measured did not provide evidence to support a metabolic advantage of low-carbohydrate diets and showed little evidence of a metabolic advantage of high-protein (>25% of energy) diets.
Is a calorie a calorie?
Ten studies of energy expenditure measured in a whole-room calorimeter have been performed; in these studies, protein intake was held constant, and the percentages of energy from fat and carbohydrate were varied (38–47). The fat content of the low-fat diets used in these studies ranged from 3% to 20% of energy, and the fat content of the high-fat diets ranged from 40% to 60% of energy; the protein content was held at 10%, 15%, or 20% of energy. When the protein content was held constant and fat was substituted for carbohydrate, the mean 24-h energy expenditure of the control groups did not differ. Two studies (43, 46) also included a postobese subgroup, in whom 24-h energy expenditure decreased 75–80 kcal/d after consumption of the high-fat diet. When the results of all 10 studies were averaged, the difference in 24-h energy expenditure between the high-carbohydrate and high-fat diets was not different from zero (x̄ ± SD: −19 ± 54 kcal/d).
the mechanism might not be right, but the data suggests that something is happening.

Obesity researcher Dr. Jules Hirsch suggests that the data were skewed by the loss of body water on the low-carbohydrate diet, an issue that affects many similar studies.
posted by ludwig_van at 10:50 AM on August 20, 2012 [17 favorites]


Fasting is not a panacea it is a tool. It goes along with taking care with what you put into your body, exercising, and coping with everyday stress. Judging by the tubs of American lard I passed on my way to work today we could all benefit from skipping a few meals.

It used to be that I could polish off 4-5000 calories per day without issue at all. Hell, I was a double rat in the Marines and I only put on 7 pounds.

Then I turned 35 and put on 50 lbs in 3 years.

My wife spends 5 times what I do at the gym and eats 1/3 of what I do and she struggles to maintain her weight.

You can't universalize your experience, and even if you could, it's a moving target anyway.
posted by Pogo_Fuzzybutt at 10:53 AM on August 20, 2012 [1 favorite]


ludwig_van:

Comparing isocaloric high-carb and low-carb diets misses what I suspect is the most important part: that on a low-carb diet, you increase your caloric deficit unconsciously, while on a high-carb one, you have to exert conscious willpower in the face of hunger and lethargy. It's like ("like", not "exactly like") low-carb diets treat the cause of fat gain while high-carb low-calorie diets treat only the primary symptom.

You'll find plenty of studies showing that ad libitum low-carb diets work, while I doubt you'll find any for high-carb diets.

One other thought. There hasn't been much study comparing diets when a caloric surplus is present. Based on my own experience, I wouldn't be surprised to see that one can vastly "overeat" on a low-carb diet without gaining fat, which would mean that it's possible to lose weight on a low-carb diet even when there is an overall caloric surplus, as long as there are periods of caloric deficit as well (for example, with intermittent fasting or just low-calorie days.)

Science aside, I can't tell you how effortless a low-carb ad libitum diet is for this sample size of one compared to a low-calorie, moderate-carb one. I struggled for a year to lose 12 pounds by consciously maintaining a caloric deficit. Then I lost over 50 lbs in nine months literally eating as much as it takes to make me full -- we're talking red meat, cheese, bacon, cream, butter, mayo, and lots of veggies with fatty dressings -- and very satisfied on a ketogenic diet.
posted by callmejay at 11:36 AM on August 20, 2012 [4 favorites]



Maybe you're aware of these and are looking for even longer-term studies, but studies of low-carbohydrate diets that last one year or two years demonstrate exactly what you said; that (quoting the 2-year study) "Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize."

The JAMA study by Dr. Ludwig's group linked above was not only short-term, conducted on a small sample, and produced highly-variable results, but it was also a study on maintenance of a reduced bodyweight, not weight loss. All subjects in the study reduced their weight with the same standard diet, which included carbs. It's been demonstrated many times that there is no metabolic advantage inherent in a low-carbohydrate diet. The carbohydrate/insulin hypothesis of obesity, popularized in part by Gary Taubes, is not taken seriously in the field of obesity research.


Thank you for the information.
posted by KaizenSoze at 11:39 AM on August 20, 2012 [1 favorite]


Here is a quick rebuttal to your link.
posted by callmejay at 11:39 AM on August 20, 2012 [1 favorite]


Is this 5:2 diet supposed to be two consecutive days of fasting or two nonconsecutive days?
posted by pracowity at 11:53 AM on August 20, 2012


on a low-carb diet, you increase your caloric deficit unconsciously, while on a high-carb one, you have to exert conscious willpower in the face of hunger and lethargy

This seems to be how those who have had success with low-carb diets describe it. And it's great that they've found something that works for them. However, long-term studies show no greater compliance or greater weight loss with low-carb diets in general.

There hasn't been much study comparing diets when a caloric surplus is present. Based on my own experience, I wouldn't be surprised to see that one can vastly "overeat" on a low-carb diet without gaining fat, which would mean that it's possible to lose weight on a low-carb diet even when there is an overall caloric surplus, as long as there are periods of caloric deficit as well (for example, with intermittent fasting or just low-calorie days.)

There have been many studies done on experimental overfeeding, and there's no evidence for what you propose here. A chronic energy deficit always results in weight loss and a chronic energy surplus always results in weight gain, although the adaptive metabolic responses to under- and overfeeding vary between individuals, altering the "energy out" side of the equation.

Here is a quick rebuttal to your link.

Guyenet updated his post to respond to criticisms after first publishing it. He addresses Type I diabetics in the section that begins: "Now let's address the common sense arguments that are used to support the insulin hypothesis of obesity. "
posted by ludwig_van at 11:55 AM on August 20, 2012 [1 favorite]


One thing that I'm particularly interested in is distinguishing between approaches that provide for effective fat loss and those that are effective at causing weight loss.

I'd argue that approaches that the most effective approaches are those that result in high fat loss, rather than those which result in losing some amount of fat but a relatively high amount of lean body mass.

One reason (and I have no idea if this is actually true, and is why I'm curious about this) is that I've heard that a benefit of spreading meals throughout the day while creating a caloric deficit is to limit the amount of lean body mass that's lost. I guess the logic goes something like "If you are fasting, the body will begin to cannibalize muscle for energy at some point, so it's better not to fast." I don't know if there's any scientific basis for that idea or not, and I'd be interested in finding out.

If it turned out that, yes, a fasting approach like this resulted in weight loss, but a significant amount of the weight lost turned out to be lean body mass...well, then it's probably an approach I'd not be so excited about.
posted by MoonOrb at 12:22 PM on August 20, 2012 [1 favorite]


MoonOrb: From what I've read in terms of actual studies, intermittent fasting (12-24 hours) with caloric restriction actually winds up no worse, and often significantly better than, frequent small meals with caloric restriction. Intermittent fasting, at least in rats, seem to produce many of the longevity benefits of caloric restriction without restricting overall calories.
posted by Earl the Polliwog at 12:25 PM on August 20, 2012


There have been many studies done on experimental overfeeding, and there's no evidence for what you propose here.

Do you know of any that used a ketogenic diet? I'd be really interested to see one.

Guyenet updated his post to respond to criticisms after first publishing it. He addresses Type I diabetics in the section that begins: "Now let's address the common sense arguments that are used to support the insulin hypothesis of obesity. "

I'm honestly not qualified to adjudicate this matter. I'd probably be on your side if I didn't experience the difference for myself. I realize that I sound like a credulous ignoramus, and the skeptical side of me is well-aware of that, but the change since I started the diet has been subjectively so vast that it's hard for me to believe it's not just a sneaky way to cut calories.

Before, I would be constantly hungry, feeling weak and tired and sad only a few hours after every meal or snack, needing to choose between gaining weight constantly and not feeling like shit. Now I feel consistently good and steady and lose weight effortlessly. There just has to be something to it more than calories.
posted by callmejay at 12:28 PM on August 20, 2012


(I mean "it's hard for me to believe it IS just a sneaky way to cut calories.")
posted by callmejay at 12:29 PM on August 20, 2012


MoonOrb: the wikipedia page on "starvation mode" says that our bodies begin burning muscle only after the fat reserves have been exhausted. So I would imagine it would take quite a number of days of not eating anything for the average person to begin to burn muscle for fuel.
posted by Baethan at 12:44 PM on August 20, 2012


Baethan, that can't be the case. See: every lifter or bodybuilder who has been on a caloric deficit and monitored their body composition. You essentially always lose some muscle if you lose weight, although high protein intake and intermittent fasting may be able to somewhat reduce that proportion.
posted by Earl the Polliwog at 12:50 PM on August 20, 2012 [1 favorite]


Thanks for the responses.
Baethan, I'm not quite sure if I agree with that analysis, though, since even when you're on a plan where you're eating six times (or more) a day, it's almost impossible to avoid losing some lean body mass if you are in a caloric deficit. I'm wondering what research is out there that would help those people who want to minimize the amount of LBM that's lost when in a caloric deficit, and I find a lot of research doesn't help as it just measures "weight loss." It could be that IF is a great approach to this; it just runs counter to the "one reason to eat frequently is to minimize cannibalizing LBM" advice I've heard before. So I'd love to know some actual research.

On preview: Earl the Polliwog said it better than I have.
posted by MoonOrb at 12:55 PM on August 20, 2012


Well now I'm fascinated/horrified. Are there any good sources that explain how that works? I tried a google search on it of course but came up with mostly Yahoo answers and ebooks for sale.
posted by Baethan at 12:59 PM on August 20, 2012


wrt iviken's post above, esp. addressing the NPR link's claim that "it is easy for some people to overeat, especially if they're not concerned about their health."

Yeah, *some* people. Fasting is as much of a diet as any other type of diet. The NPR article, as well as the other ones cited, references people who are fasting for the first time or people who are new at it. Certainly, for those new to the practice, this was not a good year to fast ;)

If one eats too much when it comes time to break the fast, the body will--invariably--experience some sort of adverse reaction. One huge tip towards a healthy and sustainable fast (especially during ramadan) is to ease out of eating when it is time to fast and ease in to eating when it is time to break the fast.

Specifically during ramadan, the fast isn't broken with copious amounts of food right off the bat. It's usually a date, a glass of water (or two), a bit of milk and a couple small pieces of ginger. And then it's off to say prayer. And THEN it's time for a proper meal. I do find myself eating a lot less during the month (approximately half my usual amount).
posted by raihan_ at 1:07 PM on August 20, 2012 [2 favorites]


The body is not so quick to use muscle for energy.

Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?
Results reveal similar weight loss and fat mass loss with 3 to 12 weeks' intermittent CR (4-8%, 11-16%, respectively) and daily CR (5-8%, 10-20%, respectively). In contrast, less fat free mass was lost in response to intermittent CR versus daily CR.
Before, I would be constantly hungry, feeling weak and tired and sad only a few hours after every meal or snack, needing to choose between gaining weight constantly and not feeling like shit. Now I feel consistently good and steady and lose weight effortlessly. There just has to be something to it more than calories.

That's great, no sarcasm. To be clear, I'm not disputing your results or telling anybody to change the way they eat. I've just seen a lot of people jump to (and then perpetuate) flawed conclusions based on their personal experiences, and I've seen this sometimes lead to unrealistic expectations or decisions being made based on inaccurate models, which doesn't help anyone.

The question of why you and certain other individuals respond better to a low-carb or ketogenic diet than to other approaches is a valid one. Stephan Guyenet of Whole Health Source has written a lot about Food Reward, which seems to be a good fit for the data. In short, this theory says that obesity is the result of our biology interacting with a food environment very different from the one in which it evolved, in which energy-dense, highly-palatable foods are always available. The body's regulatory system doesn't know how to cope with this, resulting in an increase in fat stores, moreso in people with certain genes. The beneficial effects of low-carb diets then are the result of the satiety effect of dietary protein as well as the removal of many highly-palatable, obesogenic "problem foods" by default.

But it seems fairly clear at this point that the problem of obesity is not about carbohydrates per se, so I see eliminating carbs as throwing out the baby with the bathwater in many cases. And any kind of rigid, food-avoiding diet that encourages black and white "clean" vs. "dirty" thinking tends to have higher failure rates and is more likely to lead to disordered eating patterns (1, 2).
posted by ludwig_van at 1:08 PM on August 20, 2012 [5 favorites]


FFS, most of the programme is this tedious man wittering on about himself. There are so many supposedly factual programmes on the BBC these days which seem to be pretexts for the presenter telling us how they feel about things, which I couldn't care less about. They could edit it down and get the actual information into about five minutes.

By the way, I'm assuming that the 500 calories is the total allowed - that if one does a run that burns 300 calories, it's ignored, rather than offset against the food intake (so allowing up to 800 calories). Yes?
posted by Grangousier at 1:45 PM on August 20, 2012


Much of the fasting literature has largely ignored sex differences. Unfortunately, most studies are done on male subjects; and it turns out there may be some interesting differences worth paying attention to.

Stefani Ruper put together a coherent, well-researched blog post that points out where men and women differ in mood, insulin, and metabolic responses to intermittent fasting. In short, women generally may not exhibit many of the same benefits to fasting that are found in men. It's an impressive read and provides food for thought.
posted by nicodine at 1:50 PM on August 20, 2012 [5 favorites]


If anyone else's eyes hurt just looking at Ruper's post, a guy named Mark who sounds like he knows about fasting has an article that responds to Ruper. I can't speak for how well it summarizes what Ruper has to say (because ow my eyes) but it sounds pretty reasonable.
posted by Baethan at 2:49 PM on August 20, 2012 [2 favorites]


I read pretty close the post which claims to debunk the carbohydrates cause obesity hypothesis (CCOH). He concludes thusly:

I hope you can see by now that the carbohydrate hypothesis of obesity is not only incorrect on a number of levels, but it may even be backward. The reason why obesity and metabolism researchers tend not to take this idea seriously is that it is contradicted by a large body of evidence from multiple fields. I understand that people like ideas that "challenge conventional wisdom", but the fact is that obesity is a complex state and it will not be shoehorned into simplistic hypotheses.

I do not see this. In particular this statement: "obesity is a complex state and it will not be shoehorned into simplistic hypotheses"; to me it seems this is as true in regards to the CCOH as it is equally true in regards to that blogger's (-1)*CCOH.

The last time I took a lot of time to dig into these topics I found this graphic depiction of Map of the major metabolic pathways in a typical cell. In my browser I have to zoom that sucker about 3X before I can make out any of the details. Any reductionistic argument which isolates one or two or three or four of these chemical pathways is doomed. If people find one simple fix that helps them, to me the only thing that shows is they happened upon the worst error they were making in their habits before they stumbled upon that particular fix.
posted by bukvich at 4:14 PM on August 20, 2012 [1 favorite]


This guy has the best arguments debunking Taubes and the paleo diet guys I have found.
posted by bukvich at 5:10 PM on August 20, 2012 [1 favorite]


Fasting you say?

Swankee on fasting because the world needs more reasons to post to Ray.


the past on The Blue
posted by rough ashlar at 5:16 PM on August 20, 2012 [1 favorite]


This is a really interesting FPP, MighstAllCruckingFighty. Thank you for posting it.

I was extremely skeptical when the documentary began, but it kind of won me over by the end. Don't know if I could sustain a 5:2 diet, but it might be worth a try for awhile!
posted by Kevin Street at 6:15 PM on August 20, 2012



Hmm interesting. Looks like I naturally follow this way of eating anyways. I regularly have days where I just don't eat or eat very little. Today for instance all I ate was a bowl of tomato soup and I worked an 8 hour shift waitressing without any problems with energy of hunger pains. Some days I just don't feel like eating. Most other days if I did that I would be ravenous and tired.

I should keep track and see how often it occurs.
posted by Jalliah at 11:39 PM on August 20, 2012


Just chiming in as another person who has been on the 16/8 diet since November last year - initially it was really hard going until 1pm without eating but now it's just part of my routine. I've had to buy 2 new belts and have gone down 3 notches on my latest one and I've never felt better. I can almost see a six pack in the right light.

I can still eat junk food in moderation, I do maybe 10 minutes of weight training a day and that's about it. Having tried and failed on numerous other diets I can't express how happy I am with this one. I'm in it for the long haul.
posted by gronkpan at 11:40 PM on August 20, 2012 [4 favorites]


Basically with Ramadan, I know there are people who eat as heavily as possiable after sunset, but from what I understand, one is really supposed to just eat enough to
keep up with one's accustomed daily business.
Since one can't drink water or other liquids, I think thirst would be more if a problem than hunger.
Women have a number of reasons not to fast.
posted by Katjusa Roquette at 2:41 AM on August 21, 2012


None of this is surprising. Most of human history has been spent fasting which is what you do between meals. Surely our human ancestors, living off the land, experienced frequent periods of time when food was scarce and the body has over time adapted to this.


I don't think it is really plausible that the human body ever adapted in favor of a long or particularly healthy life. If a prehistoric person managed to get enough food, it doesn't seem like details of nutrition would have been particularly relevant to their evolutionary success. Does a modern person's diet significantly affect their chance of reaching even age 30 or so, outside of extremes of obesity that wouldn't have been possible for a hunter gatherer? A human would have had to be adapted to survive periods without food, certainly, but not insofar as it would have been healthy in a modern sense.

I don't think there is any good reason that a diet is going to be better if it's based on our ancestors' diet, or any other idealized diet. At least in the case of say, a "Meditteranean diet", if it is actually similar to what people that in region eat, we know that it is at least compatible with their level of health in a large group of people.

Generally conventional ideas, which tend to exclude fasting, encourage a "balanced" diet between different types of foods, etc also are at least definitely compatible with relatively good health for most people. It certainly seems possible that other things could be better, though, depending on the situation, but also that anything like that is very difficult to confirm because of the hugely complicated way diet effects a huge number of things differently in different people over long periods of time. It is certainly easier to figure out something for someone with a specific goal in mind.
posted by Raidallinen at 3:07 AM on August 21, 2012 [1 favorite]


Only a short term study, each diet was tried for four weeks. The problem is the long term maintenance.

There will never be a [safe] diet that keeps working after people stop doing it. They will always gain back weight if they go back to their old ways of eating.

Does nobody else become an angry monster without enough food?

I think the problem for a lot of people is the transition from running off of the food they have eaten and into using fat reserves. If you are on a normal calorie restricted diet, this happens multiple times a day. If you are fasting, it happens once at the beginning of the fast period. This is also why people find low-carbohydrate diets easier; there is no difference, mood-wise, between running off of one's own protein and fat and some other animal's protein and fat.
posted by gjc at 7:11 AM on August 21, 2012 [1 favorite]


Any benefits he got from the fast, he lost when he mixed his cup-a-soup with a HOTEL PEN.

Seriously, hasn't he ever watched one of those 20/20 specials?
posted by condour75 at 9:13 AM on August 21, 2012 [1 favorite]


"By the way, I'm assuming that the 500 calories is the total allowed - that if one does a run that burns 300 calories, it's ignored, rather than offset against the food intake (so allowing up to 800 calories). Yes?"

I think he's just saying that you eat no more than 500-600 calories on two non-consecutive days of the week, and that's it. There's no futzing the total by subtracting calories burned through exercise or whatnot.

But if one does engage in regular exercise, the health effects would no doubt be even more pronounced. And I think it's implied that Mosley reduced the amount of protein in his diet even on non-fasting days, to bring down his IGF-1 level.
posted by Kevin Street at 10:40 AM on August 21, 2012


I'm coming late to this, but: I've been fasting one day (sometimes two) per week, for about the last five months. It's been very interesting, and I think beneficial, in terms of pushing out the boundaries of what I consider deal-with-able as far as physical discomfort goes, or as mr. ersatz put it, above:
I suspect that regular fasting also has the psychological side-effect of helping develop self-awareness, willpower and discipline that can be applied on non-fast days.

Most certainly, yes!

The other fun thing is the day after fasting, when I first eat or drink something, and I'm like "HOLY SHIT EATING FOOD IS SO FUCKING AWESOME FUCK FUCK FUCK YES"

Anyway, I had to stop and double-check to see if it's really been five months; it certainly hasn't negatively impacted my life such that I've been dreading each week's fast day. It feels totally normal, now, and feasible, and I kinda look forward to fast days now, as a slightly different mode of being.
posted by Greg Nog at 2:15 PM on August 24, 2012


Debunking the hunter gatherer workout.
posted by bukvich at 11:33 AM on August 25, 2012


Debunking the hunter gatherer workout.

I read that study with interest when it was published, and I still can't make sense of its findings.

My understanding, which is supported by this article: they found that after adjusting for body mass (as the Hadza are generally smaller than westerners), the two groups tend to expend a similar amount of energy each day. But the Hadza are significantly more physically active, and they burn the same amount of energy while resting and while walking.

I don't know how these facts can be reconciled, and this article doesn't seem to explain it. It says:
We think that the Hadzas’ bodies have adjusted to the higher activity levels required for hunting and gathering by spending less energy elsewhere. Even for very active people, physical activity accounts for only a small portion of daily energy expenditure; most energy is spent behind the scenes on the myriad unseen tasks that keep our cells humming and our support systems working.
So when they say "spending less energy elsewhere," they mean to suggest that the Hadza use less energy on their basal metabolism. But the immediately preceding paragraph says:
It’s not that their bodies are more efficient, allowing them to do more with less: separate measurements showed that the Hadza burn just as many calories while walking or resting as Westerners do.
So yeah, I don't get it. I'd love it if someone who sees what I'm missing could explain.
posted by ludwig_van at 6:36 PM on August 26, 2012


Thanks for the link to the study ludwig_van.

If you look at their scatter plot figure 1 (Individual comparisons of TEE and FFM) it doesn't look to me like a high reliability claim. Except it's a negative claim. I would be much more surprised if they had this level goodness of fits and claimed they supported the idea that the Hadzas burn a lot more energy in everday life routine than we westerners do.

I think the inference they are making is Hadzas burn more energy sitting and lying down than we do; isn't this very similar to the fitness guys who routinely claim that a muscular 200 pound body burns far more calories than a fatty 200 pound body? The Hadzas have very low body fat percentages.
posted by bukvich at 3:19 PM on August 28, 2012


I think the inference they are making is Hadzas burn more energy sitting and lying down than we do

It would only make sense if they were claiming that the Hadza burn less energy at rest than westerners, since they do more physical activity but have similar total energy expenditure. And that seems to be what they're suggesting when they say "We think that the Hadzas’ bodies have adjusted to the higher activity levels required for hunting and gathering by spending less energy elsewhere" (from the article) and "Estimated physical activities levels (PAL, calculated as TEE/estimated BMR), suggest that Hadza adults spend a smaller portion of TEE on BMR than Westerners" (from the study).

However, they measured the energy expenditure of the Hadza while walking and while resting using a respirometer, and reported that: "The energy cost of walking (kCal kg−1 m−1) for Hadza adults was well within the range of values reported for Western subjects ... RMR for Hadza adults measured while sitting averaged 11% above predicted BMR [27], within the range of values (7–35%) reported for other populations."

I can't figure out how these findings are not contradictory.

isn't this very similar to the fitness guys who routinely claim that a muscular 200 pound body burns far more calories than a fatty 200 pound body

No. That's an accurate claim; BMR is highly correlated with fat free mass. But that's not what's going on here. The Hadza men average 50.9 kg (at 13.5% bodyfat, so ~44kg lean), compared to the 81 kg average for western men (at 22.5% bodyfat, so around 63kg lean). Since the westerners are so much larger than the Hadza, we'd expect them to have higher energy expenditures -- and they do, averaging 3053 kcal/day to the Hadza's 2649. But the surprising finding of this study is that after controlling for body mass, the energy expenditures are similar, despite the Hadza doing significantly more physical activity. So, they infer, obesity in westerners is not related to a lack of physical activity.
posted by ludwig_van at 7:34 AM on August 29, 2012


Severe Diet Doesn’t Prolong Life, at Least in Monkeys
posted by homunculus at 6:12 PM on August 29, 2012


Has anyone been trying this 5:2 diet out? It's only been two weeks so it's still hard to tell whether it's sustainable or effective. But it seems relatively painless. The knowledge that you can eat whatever you want if you just wait until tomorrow is a nice motivation to stick through a fast day. I'm still skeptical, but I'm apparently down 3 pounds despite eating with reckless abandon the entire long weekend, so maybe there's something to this.
posted by naju at 7:49 AM on September 4, 2012


I've lost three kilos in three weeks by doing this. I know this is just one data point, I'm not sure if there have been any proper studies. It seems a lot easier for me as well to maintain than other diet changes I've attempted before. On my eating days I've found myself not going as crazy with food as I thought I would.
posted by MighstAllCruckingFighty at 5:28 AM on September 6, 2012 [1 favorite]


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