Patients with Obesity: Baseline Body Composition, Follow-Up Retention, and Longitudinal Changes—A Single-Center Real-World Study

Aim: Using real-world data from an obesity clinic, we aimed primarily to define the body composition phenotype associated with increasing obesity severity and to quantify follow-up retention and clinically meaningful weight loss. As a secondary exploratory objective, we also examined how diabetes mellitus (DM) relates to these patterns beyond BMI. Methods: Among 5350 screened adults in the Obesity Clinic database, 2879 eligible individuals were included in the baseline cross-sectional analyses, including a non-obese comparison subgroup with BMI < 30 kg/m2. The longitudinal cohort comprised 730 patients with obesity who returned for regular follow-up and had repeat BIA measurements at least 6 months after baseline. Patients were classified according to BMI and glycemic status. Results: Increasing BMI was associated with higher glucose, HbA1c, uric acid, triglyceride, C-reactive protein, and leukocyte levels and with lower HDL cholesterol. Body composition deterioration was driven predominantly by disproportionate increases in visceral fat score, fat mass, and total fat-to-muscle ratio rather than by parallel gains in muscle compartments. As obesity severity increased, the proportion of patients with diabetes also increased. Only 29.3% of the baseline obesity cohort achieved regular 6-month follow-up, and 79.0% of those followed lost less than 5% of baseline body weight. In age- and sex-adjusted analyses, the most pronounced DM-related body composition differences were observed in the BMI 30–39.9 kg/m2 group, particularly through higher waist-to-height ratio and total fat-to-muscle ratio. Conclusions: This study shows that increasing obesity severity is accompanied by a more adverse metabolic profile and a body composition pattern characterized by greater adiposity. Within this framework, diabetes-related body composition differences were not homogeneous across BMI categories and appeared to be most evident in the BMI 30–39.9 kg/m2 group. The weaker association observed in the BMI ≥ 40 kg/m2 group may be related to the reduced discriminative value of waist-based measures in severe obesity, where fat accumulation may extend across multiple compartments. Given the low continuity of follow-up and the limited rates of clinically meaningful weight loss, these findings support a more refined phenotyping approach in obesity management that incorporates body composition and fat distribution in addition to BMI.