Evenly Distributing Daily Dietary Protein Across Three Meals Reduces Women's Snack Food Reinforcement and Intake of Energy-Dense Snack Foods During Weight Loss: A Randomized Controlled Trial.

BACKGROUND

High-protein, energy-restricted diets support weight loss and maintenance; however, whether consuming a moderate amount of protein in a balanced distribution throughout the day reduces the reinforcing value (RV) and energy intake of energy-dense snack foods is not known.

OBJECTIVE

This study aimed to assess the effect of 2 patterns of protein distribution during weight loss on (1) the relative reinforcing value (RRV) of energy-dense snack foods compared with the RV of a nonfood alternative; (2) energy intake when presented with snack foods; and (3) potential moderators of adherence to a weight-loss diet, including food-related motivations, attitudes, and behaviors.

DESIGN

This was a 16-week randomized parallel study testing 2 patterns of daily protein intake: even distribution across 3 meals (EVEN) vs a skewed distribution with most protein consumed at dinner (SKEWED).

PARTICIPANTS/

SETTING

Healthy community-based women aged 20 to 44 y with a body mass index (BMI) of 28 to 45 were recruited from the greater Grand Forks, ND, area between October 2017 and April 2023; study activities were suspended from March 2020 through May 2022 during the COVID-19 pandemic.

INTERVENTION: Participants completed an 8-week weight loss phase (20% energy restriction, all foods provided), followed by an 8-week self-choice phase with instructions to maintain their assigned protein distribution pattern and energy intake.

MAIN OUTCOME MEASURES: RRV was assessed at baseline, week 8, and week 16 using an operant responding computer task 2 hours after eating a lunch consistent with the assigned protein distribution (EVEN 35 g; SKEWED 20 g).

STATISTICAL ANALYSIS: Data from 44 participants who completed the study were analyzed using a linear mixed model analysis of variance.

RESULTS

The RRV of energy-dense snack foods was lower (P = .0476) in the EVEN group (0.44 ± 0.04) than in the SKEWED group (0.55 ± 0.04). In this study, an RRV score >0.5 signified a greater reinforcing value for energy-dense snack foods than for the preferred sedentary activity. Although the amount of snacks earned did not differ between groups (P = .2338), the EVEN group consumed less than the SKEWED group (44.3 ± 5.2 g vs 62.0 ± 5.1 g; P = .0197).

CONCLUSIONS

Lower RRV and consumption of energy-dense snack foods in the EVEN group are consistent with differences in food-related motivation and satiety associated with protein distribution across meals. These findings may help refine dietary strategies aimed at supporting weight loss efforts among women.