Can an Eight-Week Exercise Program for Young Women with Normal-Weight Obesity Improve Body Composition, Cardiorespiratory Fitness, and Selected Cardiometabolic Markers? A Randomized Controlled Trial

Background: Body mass index (BMI) screening may fail to identify normal-weight obesity (NWO) despite excess adiposity and unfavorable metabolic profiles. Methods: In this randomized trial, 30 women (aged 20–39 years; BMI 18.5–24.9 kg/m2, body fat ≥ 30%) were assigned to supervised exercise or non-exercise control groups. The exercise group trained three days per week for eight weeks. Body fat percentage was the primary outcome. Secondary outcomes included body mass, BMI, fat mass, fat-free mass, skeletal muscle mass, VO2max, fasting glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and lipid profile. High-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor alpha (TNF-α) were exploratory outcomes. Results: Baseline-adjusted analysis of covariance showed lower post-intervention body fat percentage (adjusted difference, −2.15 percentage points; 95% confidence interval [CI], −2.75 to −1.56; p < 0.001) and fat mass (−1.38 kg; 95% CI, −1.73 to −1.04; p < 0.001) in the exercise group. Bioimpedance-estimated fat-free mass and skeletal muscle mass and VO2max were higher. Secondary analyses favored exercise for insulin, HOMA-IR, triglycerides, and high- and low-density lipoprotein cholesterol, without multiplicity adjustment. Raw-scale hs-CRP and TNF-α differences were nonsignificant; log-transformed findings were not fully robust to leave-one-out sensitivity analyses. Attendance was 90.0% (324/360 sessions), with no dropouts or prespecified exercise-related adverse events. Conclusions: Combined aerobic and resistance exercise program improved body composition and cardiorespiratory fitness in young women with NWO, with favorable changes in selected secondary cardiometabolic outcomes. These benefits warrant assessment beyond body weight and BMI, considering body composition, cardiorespiratory fitness, and cardiometabolic markers.