Increased Protein Consumption during the Day from an Energy-Restricted Diet Augments Satiety but Does Not Reduce Daily Fat or Carbohydrate Intake on a Free-Living Test Day in Overweight Women

Abstract

Background: Higher-protein (HP) energy-restriction diets improve weight management to a greater extent than normal-protein (NP) versions. Potential mechanisms of action with regard to assessment of eating behaviors across the day have not been widely examined during energy restriction.Objectives: The objectives of this study were to test whether the consumption of an HP energy-restriction diet reduces carbohydrate and fat intakes through improvements in daily appetite, satiety, and food cravings compared with NP versions and to test whether protein type within the NP diets alters protein-related satiety.Methods: Seventeen overweight women [mean ± SEM age: 36 ± 1 y; body mass index (kg/m2): 28.4 ± 0.1] completed a randomized, controlled-feeding crossover study. Participants were provided with the following ∼1250-kcal/d energy-restricted (-750-kcal/d deficit) diets, each for 6 d: HP [124 g protein/d; 60% from beef and 40% from plant sources (HP-BEEF)] or NP (48 g protein/d) that was protein-type matched (NP-BEEF) or unmatched [100% from plant-based sources (NP-PLANT)]. On day 6 of each diet period, participants completed a 12-h testing day containing repetitive appetite, satiety, and food-craving questionnaires. On day 7, the participants were asked to consume their protein requirement within each respective diet but were provided with a surplus of carbohydrate- and fat-rich foods to consume, ad libitum, at each eating occasion across the day. All outcomes reported were primary study outcomes.Results: The HP-BEEF diet reduced daily hunger by 16%, desire to eat by 15%, prospective food consumption by 14%, and fast-food cravings by 15% but increased daily fullness by 25% compared with the NP-BEEF and NP-PLANT diets (all P < 0.05). However, consuming more protein throughout the day did not reduce the energy consumed ad libitum from the fat- and carbohydrate-rich foods (HP-BEEF: 2000 ± 180 kcal/d; NP-BEEF: 2120 ± 190 kcal/d; NP-PLANT: 2070 ± 180 kcal/d). None of the outcomes differed between the NP-BEEF and NP-PLANT treatments.Conclusions: Although appetite control, satiety, and food cravings improved after an HP energy-restriction diet, increased protein consumption did not reduce carbohydrate and fat intakes throughout the free-living test day in overweight healthy women exposed to highly palatable foods. This trial was registered at clinicaltrials.gov as NCT02614729.

Keywords: ad libitum; energy restriction; food choice; high-protein diets; satiety.

Conflict of interest statement

Author disclosures: JAG, no conflicts of interest. KCM and HJL serve on the speaker board for the National Cattlemen’s Beef Association. The Beef Checkoff supplied the funds to complete the study but was not involved in the design, implementation, analysis, or interpretation of data.

© 2017 American Society for Nutrition.

Figures

FIGURE 1

Hunger (A) and fullness (B) responses throughout the day 6 clinical testing day after the study treatments in healthy, overweight women. Values are means ± SEMs,n = 17. The solid diamonds on the x axes represent eating occasions. Bars without a common letter differ, P < 0.025. HP-BEEF, higher-protein beef diet (60% of protein from beef and 40% from plant sources); NP-BEEF, normal-protein diet (60% of protein from beef and 40% from plant sources); NP-PLANT, normal-protein plant diet (100% of protein from plant sources).

FIGURE 2

Desire to eat (A) and prospective food consumption (B) throughout the clinical testing day 6 after the study treatments in 17 healthy, overweight women. Values are means ± SEMs, n = 17. The solid diamonds on the xaxes represent eating occasions. Bars without a common letter differ,P < 0.025. HP-BEEF, higher-protein beef diet (60% of protein from beef and 40% from plant sources); NP-BEEF, normal-protein diet (60% of protein from beef and 40% from plant sources); NP-PLANT, normal-protein plant diet (100% of protein from plant sources).