Long‐Term Impact of Bariatric Surgery and Dietary Interventions on Weight Loss, Physical Activity, and Food Preferences

OBJECTIVE: This study aimed to examine changes in dietary intake, physical activity, appetite, and weight following laparoscopic adjustable gastric banding (LAGB), sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and dietary intervention in adults with severe obesity. METHODS: This prospective, nonrandomized cohort included 57 adults undergoing LAGB (n = 11), SG (n = 21), RYGB (n = 7), or dietary intervention (Diet; n = 18). Seven assessments over 36 months were analyzed using mixed-effects models. RESULTS: During the first 12 months, energy intake declined across groups (β = -1322 kJ/visit; 95% CI: -2045, -599; p < 0.001), without between-group differences in energy or macronutrient trajectories. Vigorous activity increased following SG relative to Diet (interaction β = +10 min/day/visit; 95% CI: 0.1, 20). During 12-36 months, energy intake increased in Diet (β = +3089 kJ/visit; p < 0.001), whereas surgical groups maintained energy restriction (all interactions p ≤ 0.006). Changes in macronutrients, calcium intake, and physical activity were modest or transient, although protein intake increased after LAGB relative to Diet (interaction β = +8.6 percentage points; p = 0.006). SG produced sustained appetite reduction (p ≤ 0.013). At 36 months, weight remained 25.1%, 26.4%, and 16.9% below baseline following SG, RYGB, and LAGB, respectively. CONCLUSIONS: Interventions demonstrated biphasic dietary and behavioral adaptation. Surgical procedures produced durable energy restriction and weight loss despite modest long-term changes in dietary composition and physical activity. TRIAL REGISTRATION: ANZCTR: 12613000188730.