Nutritional and Metabolic Trajectories up to 10 Years After Metabolic and Bariatric Surgery: A Tertiary-Centre Retrospective Longitudinal Cohort Study
TL;DR
Within a structured service with high supplement compliance, frank deficiency was uncommon for most markers, and these findings support indefinite, systematic nutritional surveillance after MBS.
Abstract
Background/Objectives: Metabolic and bariatric surgery (MBS) is the most effective durable treatment for severe obesity but predisposes to micronutrient deficiency. Long-term, broad-panel biochemical data are scarce. We examined nutritional and metabolic trajectories over up to 10 years and compared sleeve gastrectomy (SG) with Roux-en-Y gastric bypass (RYGB). Methods: Retrospective single-centre cohort undergoing MBS (NHS Lothian, 2011–2025). Twenty-five biochemical markers were captured at baseline, 6 months, 1, 5 and 10 years, and analysed using linear mixed-effects models adjusted for procedure, sex, age, baseline BMI, diabetes and deprivation, with Benjamini-Hochberg correction. Results: Of 458 patients, 426 were analysed (82.4% female; median age 49 years; median baseline BMI 44.2 kg/m2; SG 55.2%, RYGB 41.1%; median follow-up 7.0 years). Median total and excess weight loss were 21.6% and 49.2%. Pre-operative type 2 diabetes affected 99/422 (23.5%), resolving in 41 (41.4%). Adjusted calcium fell (p < 0.001) and parathyroid hormone (PTH) rose (+0.22 pmol/L/year [95% CI 0.11, 0.33], p < 0.001) despite vitamin D increasing (+1.20 nmol/L/year, p < 0.001); elevated PTH persisted in ~33%. Haemoglobin declined (−0.32 g/L/year, p = 0.026), below-range values rising from 26.3% (109/415) to 38.5% (84/218). Serum iron and transferrin saturation rose (p = 0.034; p = 0.002). B-vitamins increased (all p < 0.001) except thiamine. Selenium, red-cell selenium and zinc fell (all p < 0.05); albumin declined (p < 0.001); cholesterol was stable. Folate and vitamin E trajectories differed between SG and RYGB; other markers did not. The PTH rise was steeper with proton pump inhibitor use (p = 0.002) and baseline BMI ≥ 50 kg/m2 (p = 0.003). Conclusions: Within a structured service with high supplement compliance, frank deficiency was uncommon for most markers. Nonetheless, progressive biochemical changes emerged and persisted, most consistently falling calcium with rising PTH and declining haemoglobin. These findings support indefinite, systematic nutritional surveillance after MBS.