Examination of Protein Quantity and Protein Distribution across the Day on Ad Libitum Carbohydrate and Fat Intake in Overweight Women

Abstract

Background: The effects of meal-specific protein quantity and protein distribution throughout the day on daily food intake are relatively unknown. Objectives: The aims were to test 1) whether the consumption of higher-protein (HP) compared with normal-protein (NP) meals consumed at each eating occasion reduce free-living, daily carbohydrate and fat intakes in overweight women during energy balance conditions and 2) whether the distribution of protein consumed throughout the day affects food intake outcomes. Methods: Seventeen women [mean ± SEM age: 33 ± 1 y; body mass index (in kg/m2): 27.8 ± 0.1] completed the following tightly controlled, crossover design study. Participants were provided with and randomly consumed three 6-d eucaloric diets containing NP or HP (15% or 25% of energy as protein, respectively). The protein content within the NP diet used an even distribution pattern (EVEN; 21 ± 1 g protein/meal) throughout the day, whereas the protein contents within the HP diets used either EVEN (35 ± 1 g protein/meal) or an uneven distribution pattern (UNEVEN; 19 ± 1 g protein/breakfast, 26 ± 1 g protein/lunch, 63 g protein/dinner). On day 7 of each diet, the participants were asked to consume the diet-specific absolute protein quantity (in grams) at each eating occasion but were provided with a surplus of carbohydrate- and fat-rich foods to consume, ad libitum, during each eating occasion. Results: Eating more protein (HP compared with NP) or evenly distributing protein throughout the day (HP-EVEN compared with HP-UNEVEN) did not reduce the consumption of ad libitum fat- and carbohydrate-rich foods throughout the day (NP-EVEN: 2850 ± 240 kcal/d; HP-EVEN: 2910 ± 240 kcal/d; HP-UNEVEN: 3160 ± 200 kcal/d). Despite the lack of differences in daily energy intake, the breakfast meal within the HP-EVEN diet led to lower ad libitum carbohydrate and fat intakes than the breakfast meals in the NP-EVEN and HP-UNEVEN diet conditions (P < 0.05). Conclusion: Providing 30 g protein/meal at each eating occasion throughout the day did not influence free-living, daily intake of highly palatable, carbohydrate- and fat-rich foods in overweight women. This trial was registered at clinicaltrials.gov as NCT02614729.

Keywords: ad libitum; food choice; food intake; high-protein diets; overweight; protein distribution; women.

Figures

FIGURE 1

Energy consumed at each eating occasion after the protein-specific requirements, depicted as NP-EVEN (light-gray bars), HP-EVEN (black bars), and HP-UNEVEN (dark-patterned bars). Repeated-measures ANOVA with post hoc pairwise comparisons was used. Bars without a common lowercase letter differ, P < 0.05. *NP-EVEN compared with HP-EVEN, P = 0.06. EVEN, even distribution pattern; HP, higher-protein; NP, normal-protein; UNEVEN, uneven distribution pattern.