Can probiotics influence adaptive thermogenesis induced by continuous energy restriction following a 12-week intervention in adult men living with obesity? A secondary analysis of a randomized clinical trial (ECOMI-SP).

Background: Adaptive thermogenesis represents a metabolic adaptation that reduces energy expenditure beyond what is expected from changes in fat-free mass (FFM) and fat mass (FM) following continuous energy restriction (CER). This phenomenon may impair long-term weight loss maintenance. Emerging evidence suggests that modulation of the gut microbiota may influence energy metabolism, yet the impact of probiotic supplementation on adaptive thermogenesis in humans remains unclear.

Objectives: This study aimed to investigate whether probiotic supplementation could attenuate adaptive thermogenesis induced by CER in adult men with obesity over a 12-week intervention.

Methods: In this double-blind, placebo-controlled randomized clinical trial, 49 adult men (body mass index: 30.0-39.9 kg/m) were randomized to receive either CER combined with probiotics (CERPRO), or CER combined with placebo (CERPLA) for 12 weeks. The CER was set at 30% below total daily energy expenditure, which was calculated based on resting energy expenditure (REE) measured via indirect calorimetry multiplied by a physical activity factor (1.5) and adjusted for the thermic effect of food (10%). Adaptive thermogenesis was calculated as the difference between measured REE (REE) and predicted REE (REE), adjusting for body composition changes.

Results: Both groups experienced reductions in body weight, FM, and REE over 12 weeks (p<0.001), with no differences between groups (p>0.05). Adaptive thermogenesis was present in both CERPRO (-129 kcal) and CERPLA (-127 kcal) groups, with no differences between groups (p=0.966). No additive effect of probiotic supplementation was observed on REE, adaptive thermogenesis, FM or FFM.

Conclusion: Probiotic supplementation did not attenuate CER-induced adaptive thermogenesis in men with obesity. Despite substantial reductions in REE and FM, the presence of adaptive thermogenesis persisted regardless of probiotic use. These findings suggest that probiotics do not modify metabolic adaptations associated with CER in humans.