Weight change and energy balance
The most striking finding in this study was that the ad libitum low-fat, high-fiber diet induced a significant weight loss, whereas the high-mono diet did not. The statistically significant time x diet interaction for the body-weight changes indicated a differential response of body weight to the 2 diets (Table 2Go). Further analysis using Tukey’s multiple comparisons procedure indicated that weight loss was statistically significant only during the low-fat diet (–1.53 ± 1.21 kg; P < 0.001). Body weight decreased ≥1.0 kg in 8 of the 11 participants during the low-fat diet and in only 3 of the 11 subjects during the high-mono diet. Subjects were offered a mean of 3555 kcal/d during both diets (Table 3Go), which is 25% above the eucaloric energy requirement of 2848 ± 281 kcal/d. The subjects consumed 212 fewer kcal per day during the low-fat diet than during the high-mono diet (P < 0.02). The predicted difference in the weight loss between the 2 diets, based on the 212 kcal/d difference in energy intake, was –1.15 kg [assuming a total relative caloric deficit on the low fat diet of 212 kcal x 42 d = 8904 kcal, and a deficit of 3500 kcal = 1 lb (2.2 kg)]. The predicted differential weight loss was comparable to the observed difference of –1.06 kg between the 2 diets.
Weight loss was the only statistically significant difference in outcome, yet was accounted for in the calorie intake.