Daily Dietary Protein Distribution Does Not Influence Changes in Body Composition During Weight Loss in Women of Reproductive Years with Overweight or Obesity: A Randomized Controlled Trial

Background: Preservation of fat -free mass (FFM) during intentional weight loss is challenging yet important to maintain a resting metabolic rate. A balanced protein distribution of 25 - 30 g per meal improves 24-h muscle protein synthesis, which may promote FFM maintenance and greater reductions in fat mass (FM) during weight loss in women. Objectives: We aimed to determine whether the daily dietary protein distribution pattern during energy restriction in fl uences changes in body composition in women of reproductive age. We hypothesized that evenly distributing protein across meals compared with the usual intake pattern of consuming most of the protein at the dinner meal would be superior in preserving FFM while reducing FM during weight loss. Methods: Healthy women ( n = 43) aged 20 - 44 y with a BMI of 28 - 45 kg/m(2) completed a randomized parallel feeding study testing 2 patterns of daily protein intake (even distribution across all meals compared with a skewed distribution with most protein consumed at the evening meal). Participants completed an 8-wk controlled 20% energy restriction (all foods provided), followed by an 8-wk self-choice phase in which participants were asked to maintain a similar diet and dietary pattern when purchasing and consuming their own foods. Body composition was measured at baseline, week 8, and week 16. Data were analyzed using mixed models. Statistical signi fi cance was set at P < 0.05. Data are presented as differences in least squares means +/- SE. Results: No significant main effects of group or group-by-time interactions were observed. All measures exhibited the main effect of time ( P < 0.001). Overall, body weight, FFM, FM, and body fat percentage decreased 5.6 +/- 0.4, 1.0 +/- 0.2, 4.6 +/- 0.4 kg, and 2.3 +/- 0.2%, respectively, during this 16-wk study. Conclusion: Daily dietary protein distribution at a fixed protein level does not appear to in fluence changes in body composition during weight loss in women of reproductive age.