University of Arkansas, Fayetteville Division of Agriculture


Over 30% of adults in the U.S. are obese. A primary contributor to obesity is an unhealthy diet related to imbalanced macronutrients. Diets higher in protein (PRO) rather than carbohydrate (CHO) are associated with increased energy expenditure (EE) and reduced food intake. The objective of this pilot study was to determine if protein source at breakfast influences EE in young men (n = 4; ages 18-35). Participants consumed three isocaloric (whey (WP), pea (PP), beef (BP); 275 kcal, 62% PRO, 23% CHO, 15% Fat) drinks in a randomized, crossover design study with a one-week washout period (time between the administration of each treatment to control for potential interactions). Each test day EE, appetite, and cravings were assessed at 0, 15, 30, 60, 120, 180, and 240 min following consumption. Data were analyzed using 2-way analysis of variance (ANOVA) for effects of protein source over time and one-way ANOVA for area under the curve (niAUC). Resting EE niAUC was 8% lower in BP vs PP and 5% lower vs WP. Thermic effect of feeding niAUC was 77% lower in BP vs WP; PP was 43% lower than WP. Carbohydrate oxidation was higher (31%) with PP compared to WP with no difference between BP and WP. Fat oxidation was 23% higher in WP vs BP and PP. The WP was most satiating. Participants had a higher craving for sweet foods following PP and a higher desire for snacks following BP. Food intake posttreatment was similar in calories and macronutrient distribution. Lack of significant difference among measurements suggests that protein source is not a predictor of postprandial EE, appetite response, or food intake.