Effect of a Defined Intake of a Soy-Based Protein-Rich Supplement on Body Composition and Eating Behaviour in Overweight Women: A Secondary Analysis of the ACOORH Trial

Background: High-protein dietary strategies have been shown to support weight reduction and improve body composition during lifestyle interventions. However, evidence regarding long-term dietary adaptations and their association with body composition in overweight women remains limited. This secondary analysis of the ACOORH randomised controlled trial investigated whether a protein-rich soy-based meal replacement promotes sustained dietary protein intake and favourable body composition changes in female participants. Methods: Female participants from the multicentre ACOORH RCT with complete dietary records at baseline, week 12 and week 52 were included (n = 64). Participants received either a standardised lifestyle intervention alone or the same intervention combined with a protein-rich soy–yoghurt–honey meal replacement during the first 26 weeks. Dietary intake, body composition, physical activity and muscle strength were evaluated longitudinally. Between-group comparisons, repeated measures ANCOVA and exploratory correlation analyses were performed. Results: Both groups significantly reduced daily energy intake during the first 12 weeks. However, only the intervention group increased body weight-adjusted protein intake (+0.22 ± 0.29 g/kg/day), resulting in a significant between-group difference (p = 0.004). The higher protein intake was maintained throughout the 52-week study despite discontinuation of meal replacement after week 26 (p < 0.001). Repeated measures ANCOVA demonstrated significantly greater improvements in body mass index (p = 0.04) and fat mass (p = 0.03) in the intervention group. At week 52, higher protein intake was significantly associated with lower body mass index (r = −0.253; p = 0.04), lower fat mass (r = −0.321; p = 0.01) and greater muscle strength (r = 0.292; p = 0.02), whereas no association with physical activity was observed. Conclusions: Among overweight women participating in a structured lifestyle intervention, temporary supplementation with a protein-rich soy-based meal replacement was associated with sustained increases in dietary protein intake and more favourable long-term body composition. These findings support the concept that maintaining a higher protein intake during weight reduction may contribute to improved body composition outcomes. Larger prospective studies specifically designed to investigate sex-specific effects of protein-rich dietary interventions are warranted.