Among 216 adults undergoing sleeve gastrectomy or Roux-en-Y gastric bypass, percentage total weight loss (%TWL) at 3 months strongly predicted %TWL at 1 year (incremental R² = 38.23%) and modestly at 2 years (R² = 11.75%), but lost predictive value beyond that (R² = 2.25%, p = 0.078). Paradoxically, patients who lost weight fastest early on also showed greater weight regain from 1 year onward — a finding consistent across procedure type and diabetes status, and stronger than baseline BMI as a predictor.
This preprint, not yet peer-reviewed, adds meaningful nuance to the post-bariatric monitoring literature. The dissociation between early rapid loss and long-term durability aligns with prior research suggesting that aggressive early caloric restriction may not reprogram the metabolic set-point sustainably. The regain signal is clinically important: it suggests that high early responders should not be discharged from follow-up prematurely — precisely the opposite of current practice in many programmes.
Limitations are significant: the retrospective cohort of only 216 patients carries limited statistical power for long-term subgroup analyses, and follow-up length and completeness vary. The study cannot establish causality or rule out confounders such as pre-operative diet, physical activity, or psychosocial factors. Still, the finding that a simple 3-month weight-loss measure explains nearly 40% of 1-year variance is clinically actionable — early responders warrant closer long-term surveillance, not less.