Twelve-Week Exercise Intervention for Improving Insulin Sensitivity and Body Fat Percentage in Men with Overweight and Obesity

This study examined whether a supervised twelve-week combined exercise program could improve insulin sensitivity and reduce body fat percentage in sedentary men with overweight and obesity. Fifty-six men aged 33–58 years with body mass index between 27.4 and 38.6 kg·m−2 completed a randomized controlled trial and were allocated to either a supervised exercise group (n = 28) or a usual-care control group (n = 28). The intervention combined moderate-intensity aerobic exercise and progressive resistance training performed four times per week. Primary outcomes were homeostatic model assessment of insulin resistance (HOMA-IR) and body fat percentage. Secondary outcomes included fasting glucose, fasting insulin, waist circumference, body mass, fat-free mass, and estimated VO2peak. Baseline comparability was assessed with independent-samples t tests. Intervention effects were evaluated with baseline-adjusted analysis of covariance supported by paired-samples t tests for within-group change and Pearson correlation for the attendance-response analysis. Results: Baseline values did not differ between groups (all p > 0.80). After twelve weeks, HOMA-IR decreased from 4.49 ± 0.83 to 3.09 ± 0.83 in the exercise group and from 4.54 ± 1.00 to 4.42 ± 1.05 in the control group. Body fat percentage decreased from 32.77% ± 3.91% to 29.83% ± 4.15% in the exercise group, whereas only a trivial change was observed in the control group. Significant adjusted between-group effects were found for HOMA-IR, body fat percentage, waist circumference, body mass, fasting glucose, fasting insulin, estimated VO2peak, and fat-free mass (all p < 0.001 except fat-free mass). Session attendance was positively associated with the magnitude of HOMA-IR improvement (r = 0.53, p = 0.004). A twelve-week combined exercise intervention produced clinically meaningful improvements in insulin sensitivity, adiposity, and fitness in men with overweight and obesity. The findings support structured exercise as a practical non-pharmacological strategy for early metabolic-risk reduction.