Background High-protein, low-carbohydrate diets (HP) have been reported to produce greater short-term weight loss as compared to a low-fat, low-calorie diet (LFLC). Feelings of satiety related to ketosis have been hypothesized to result in a lower caloric intake in HP diets.
Objective To investigate the effects of the HP vs LFLC diets on subjective ratings of hunger and fullness in relation to weight loss and energy intake in severely obese adolescents. We hypothesized that subjects assigned to the HP diet will lose more weight, consume fewer total calories, and report feeling more fullness and less hunger than those on the LFLC diet.
Methods Thirty-three adolescents (18 males and 15 females, mean (± SD), age 14.1 ± 1.7 years, and BMI 37.4 ± 3.8) were randomly assigned to the HP or LFLC diet for 13 weeks. Throughout the 13 weeks subjects recorded food intake and also feelings of fullness and hunger 9 times during the day using a 10 cm visual analog scale with 0 cm = ‘not at all hungry/full’ and 10 cm = ‘extremely hungry/full.’ To assess compliance with the HP diet, beta-hydroxybutyrate (βHB) levels were measured at 13 weeks.
Results HP subjects lost significantly more weight (-9.0 vs -5.1 kg, p = .01) and had higher βHB levels (2.28 vs 1.00 mmol/L, p = .002). Based upon a similar number of diet/satiety records (7.8 vs 8.7, p = .35 in HP vs LFLC, respectively), daily energy intake was not different between the groups (12.0 kcal/kg/d for HP vs 14.0 kcal/kg/d for LFLC, p = .20) and no differences in hunger or fullness were reported between groups. Weight loss did not correlate with hunger scores, nor was energy intake correlated with hunger or fullness scores or with weight loss. There was a trend for inverse correlation between weight loss and fullness scores (r = .31, p = .08), with greater fullness corresponding to less weight loss.
Conclusions Although significantly greater weight loss was achieved by subjects on the HP diet, differences in total energy intake or in perceived hunger or fullness do not appear to account for these differences. These findings suggest that alternative explanations merit consideration.
Supported by NIH Grants MO1-RR00069 (Pediatric General Clinical Research Center) and T32 DK007496 and the National Cattleman's Beef Association.
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