Metabolically Guided Walking and Plant-Based Nutrition Enhance Body Composition and Weight Loss

Sedentary behavior contributes to obesity and metabolic dysfunction, yet few interventions individualize exercise intensity using fuel-based metrics such as the respiratory exchange ratio (RER; VCO₂/VO₂). This study investigated the effects of metabolically guided walking combined with whole-food, plant-based nutrition on body composition and metabolic outcomes in sedentary overweight and obese women. Forty-four women mean age 43 years; BMI 30.1 kg·m^-2) were randomized to low-intensity continuous training (LICT; RER ≈ 0.75), moderate-intensity intermittent training (MIIT; RER ≈ 0.85), or high-intensity continuous training (HICT; RER ≈ 0.95). Following a 2-week dietary lead-in with an individualized ~200 kcal·day^-1 energy deficit, participants completed an 8-week RER-guided walking program (5 sessions·week^-1; 15-50 min·session^-1). Assessments included air-displacement plethysmography (BodPod) body composition, resting metabolic rate and substrate utilization, and oxygen uptake at the first ventilatory threshold (VT1). Data were analyzed using ANCOVA, mixed-factorial ANOVA, and Pearson correlations. Percent body fat decreased significantly across participants (<i>p</i> < 0.0001, η² = 0.827), with MIIT demonstrating the most favorable integrated outcomes. MIIT elicited the largest reductions in total body mass (-11.2%), fat mass (-25.9%), and percent body fat (-17.1%), alongside improvements in VT1 VO₂ (Δ = 1.487 ± 0.895 L·min^-1; <i>p</i> = 0.038). Resting respiratory quotient (RQ) declined in LICT and MIIT but increased in HICT, corresponding with increased fat oxidation in LICT and MIIT and reduced fat oxidation in HICT. Changes in RQ were significantly associated with changes in percent body fat (r = 0.316, <i>p</i> = 0.039). Metabolically guided moderate-intensity intermittent walking combined with whole-food, plant-based nutrition produced the most consistent improvements in adiposity, substrate utilization, and submaximal fitness, supporting the public-health feasibility of a community-deliverable, substrate-informed walking prescription.