Dietary Macronutrient Composition and Protein Concentration for Weight Loss Maintenance

Objective: To examine the association between dietary macronutrient composition and 12-month weight loss maintenance (WLM) in adults who achieved initial weight loss (≥ 5%). Methods: This prospective cohort analysis used 12-month follow-up data from the Navigating to a Healthy Weight trial. Macronutrient composition (%) was assessed using a 4-day, 24-h dietary recall. Food sources were categorized as discretionary foods, lean meat, vegetables, fruit, grains, and dairy. Primary outcomes included 12-month changes in body weight, fat mass index (FMI), waist-to-height ratio (WHtR), and hip-to-height ratio (HHtR). A nutritional geometry approach was used to examine individual and interactive associations of macronutrient intake, visualizing as response surfaces. Results: Among 1518 participants (69.8% women; mean age 45 ± 12 years), mean macronutrient composition was 20.6% protein, 33.8% fat, and 43.1% carbohydrate. Protein energy percentage was inversely associated with energy intake (β: −0.33; 95% CI: −0.39, −0.27). Response surfaces revealed that lower proportional energy from protein, diluted by high fat and/or carbohydrate, was associated with higher total energy intake and greater 12-month increases in body weight, WHtR, and HHtR, but not FMI. Consumption of discretionary food, not other food sources, increased energy intake by reducing proportional energy from protein. Conclusions: Maintaining dietary proportional energy from protein, particularly by limiting discretionary food consumption, was associated with reduced energy intake and improved WLM.