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.
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.
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.
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.
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.
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).
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.
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).
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.
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.
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.
« Older How to Eat a Watermelon Tutorial (SLYT) was made b... | What color is a mirror? [slyt]... Newer »
This thread has been archived and is closed to new comments
Buy a Shirt