Preoperative vitamin D levels correlate with weight loss after Roux-en Y gastric bypass for morbid obesity: a prospective study

Introduction: Vitamin D deficiency is a common condition in obese patients, although its causes are not completely clear. Roux-en Y gastric bypass (RYGB), which has clearly proven to be one of the most effective procedures to induce durable weight loss in morbidly obese patients, can worsen vitamin D deficiency, if patients are not supplemented. The aim of this study is to prospectively evaluate vitamin D variations after RYGB and assess a possible predictive role of basal vitamin D in weight loss surgery. Methods: 105 patients undergoing RYGBP for morbid obesity were prospectively evaluated. Biometrical data and serohematic values were collected preoperatively and at 1, 3, 6, 12 and 24 months after surgery. An oral and intramuscular vitamin D supplementation scheme (2600UI/die) was adopted for all the patients. Results: Mean preoperative vitamin D levels were below the normal range (16.21±16.26 ng/ml) and significantly correlated with mean systolic arterial pressure (p<0,036) and fasting insulin levels (p<0.03). At three months follow-up, vitamin D levels had markedly increased. A significant correlation between preoperative vitamin levels and BMI loss was found at 12 months follow-up (p<0.05). Conclusions: Morbidly obese patients usually show important vitamin D deficiency, which can completely revert with supplementation after RYGB. Preoperative vitamin D levels significantly correlate with BMI loss, thus possibly representing a predictive factor of weight loss after RYGB.