Appetite control and biomarkers of satiety with vegetarian (soy) and meat-based high-protein diets for weight loss in obese men: a randomized crossover trial.

BACKGROUND There is limited evidence with regard to the effect of different sources of protein on appetite during weight loss. Vegetarian and meat-based high-protein diets may have contrasting effects on appetite and biomarkers of protein-induced satiety. OBJECTIVE The aim was to assess appetite response to meat or vegetarian high-protein weight-loss (HPWL) diets in obese men to monitor plasma amino acid profile and gut peptide response as potential satiety biomarkers. DESIGN Twenty obese [body mass index (in kg/m²): 34.8] men participated in a dietary intervention study. After 3 d of a maintenance diet, they were provided in a crossover design with either a vegetarian HPWL (Soy-HPWL) or a meat-based HPWL (Meat-HPWL) diet for 2 wk. Both diets comprised 30% protein, 30% fat, and 40% carbohydrate, provided to measured resting metabolic rate. Body weight and the motivation to eat were measured daily. Plasma satiety biomarkers were collected during a test-meal challenge (5 h) at the end of each diet period. RESULTS Over the 2 wk, subjects lost, on average, 2.41 and 2.27 kg with consumption of the Soy- and Meat-HPWL diets, respectively [P = 0.352; SE of the difference (SED): 0.1]. ANOVA confirmed that subjectively rated hunger (P = 0.569; SED: 3.8), fullness (P = 0.404; SED: 4.1), desire to eat (P = 0.356; SED: 3.7), preservation of lean body mass (P = 0.334; SED: 0.2), and loss of percentage fat mass (P = 0.179; SED: 0.2) did not differ between the 2 HPWL diets. There were differences in absolute concentrations of ghrelin and peptide YY between the 2 HPWL diets, although the response as net area under the curve was not different. CONCLUSIONS Appetite control and weight loss were similar for both HPWL diets. Gut hormone profile was similar between the diets, which suggests that vegetarian diets can be as effective as meat-based diets for appetite control during weight loss.