Modern obesity treatment increasingly prioritizes body composition improvements and muscle preservation over simple scale weight loss, according to the Korean Society for the Study of Obesity (KSSO). Released on September 18, 2026, the organization’s latest data highlights a shift in how clinicians evaluate therapeutic success, moving past total weight reduction to focus specifically on lowering visceral and body fat while protecting lean muscle mass.
Korean Adult Obesity Trends and Abdominal Fat Risks
According to the KSSO’s “Obesity Fact Sheet 2026,” the overall obesity prevalence among South Korean adults reached 39.2% in 2024. The data shows that male obesity climbed to 51.1%, meaning more than half of adult men are classified as obese, compared to 27.7% for women. Adults in their 30s and 40s recorded high prevalence rates at 43.1% and 43.4%, respectively. Among men, the 35 to 39 age bracket registered the highest obesity rate at 59.2%, alongside a stage 2 obesity rate (BMI of 30 kg/m² or higher) of 16.0%, which is double the 7.9% rate for women in the same age group.
Abdominal obesity also disproportionately affects men, with an overall adult prevalence of 24.9% rising to 32.4% for men and 17.6% for women in 2024. Men aged 35 to 39 faced the highest abdominal obesity rate at 38.4%. While male abdominal obesity has risen consistently over the past decade, female rates have trended downward since 2019. Because visceral fat directly correlates with cardiovascular disease and metabolic disorders, medical professionals emphasize that losing total weight is insufficient if patients simultaneously sacrifice metabolically active muscle tissue.
Body Composition Changes in Recent Obesity Pharmacotherapy
As modern anti-obesity medications drive weight loss, clinical evaluations increasingly track changes in fat mass and lean mass alongside overall weight. Both semaglutide and tirzepatide have accumulated substantial clinical trial data demonstrating targeted fat reduction while managing muscle loss.
For semaglutide, marketed as Wegovy, the SEMALEAN study evaluated 106 patients who completed 12 months of treatment. Results showed an average weight loss of 12.7%, with 59% of patients achieving at least a 10% reduction and 26% achieving a 15% or greater reduction. Body fat decreased by 18.9%, and dual-energy X-ray absorptiometry (DXA) confirmed significant reductions in visceral adipose tissue. Lean mass dropped by an average of 3 kg during the first seven months before stabilizing through month 12. Consequently, the proportion of lean mass relative to total weight increased, and the prevalence of sarcopenic obesity dropped from 49% to 33% after 12 months.
For tirzepatide, marketed as Mounjaro, a DXA sub-study of the SURMOUNT-1 trial assessed 160 overweight or obese adults over 72 weeks. The analysis showed a 21.3% reduction in body weight and a 33.9% reduction in fat mass. Lean mass decreased by 10.9%, with approximately 75% of total weight loss coming from body fat and 25% from lean mass. Experts note that because these trials feature different patient populations, durations, and designs, direct comparisons between the two drugs cannot be made, though both demonstrate effective fat-focused body composition shifts.
Cardiovascular Benefits Linked to Waist Circumference Reductions
Beyond body composition, clinical trials indicate that reducing waist circumference yields measurable cardiovascular outcomes. In the SELECT trial, which evaluated overweight or obese patients with pre-existing cardiovascular disease, semaglutide reduced the risk of major adverse cardiovascular events (MACE) by 20% compared to placebo. Patients receiving semaglutide experienced an average waist circumference reduction of 7.7 cm at 208 weeks, compared to 1.3 cm in the placebo group. Subsequent analyses established a direct correlation showing that greater waist reductions translated to lower subsequent cardiovascular event risks.
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