Background: Long-term data on lifestyle interventions in severe obesity beyond 1–2 years are scarce. This case documents 4-year outcomes of Intensive Lifestyle Modification (ILM) with Meal Replacement (MR), emphasizing the relationship between muscle preservation and weight-loss sustainability.
Case Presentation: A 52-year-old Thai female (BMI 44.1 kg/m², 102 kg, 152 cm) enrolled in a structured ILM+MR program. Body composition was assessed by bioelectrical impedance analysis (BIA; Omron HBF-375) at baseline, 8 weeks, and annually for 4 years.
Results: At 4 years, weight was 53 kg (48.0% reduction), BMI 22.9 kg/m², and waist circumference 71 cm (?51 cm). Body fat decreased from 42.0% to 29.5%; muscle mass percentage increased from 19.2% to 26.8%. BIA-estimated visceral fat level fell from 30 to 6 (80% reduction). Lean mass constituted only 16.9% of weight lost at 8 weeks, below the typical 20-30%.
Conclusion: ILM+MR achieved sustained 48% weight loss with preferential fat loss and relative muscle preservation, which may support long-term maintenance by preserving metabolic rate. This case represents an upper-extreme outcome from a parent cohort (n = 702, mean loss 14.43 kg at 52 weeks) and should not be generalized. BIA-derived estimates are acknowledged as a limitation.