Comparison of the Performance of Common Measures of Weight Regain After Bariatric Surgery for Association With Clinical Outcomes

IMPORTANCE: Estimates of weight regain following bariatric surgery vary widely. OBJECTIVE: To describe weight regain after reaching nadir weight following Roux-en-Y gastric bypass (RYGB) surgery and compare weight regain measures for association with outcomes. DESIGN, SETTING, AND PARTICIPANTS: Prospective cohort study of 2458 adults who underwent bariatric surgery at 10 hospitals in 6 US cities between March 2006 and April 2009. Assessments were conducted within 30 days’ presurgery, at 6 months’ postsurgery, and then annually until January 2015. Of the 1703 participants who underwent RYGB surgery, 1406 (83%) were followed up for 5 years or longer and had 5 or more weight measurements (excluding those who died or underwent surgical reversal). EXPOSURES: Weight regain assessed by 5 continuous measures (weight in kilograms, body mass index [BMI], percentage of presurgery weight, percentage of nadir weight, and percentage of maximum weight lost) and 8 dichotomous measures (per established thresholds) were compared in relation to clinical outcomes based on statistical significance, magnitude of association, and model fit. MAIN OUTCOMES AND MEASURES: Progression of diabetes, hyperlipidemia, and hypertension and declines in physical and mental health–related quality of life and satisfaction with surgery. RESULTS: Among the 1406 participants who underwent RYGB surgery, the median age was 47 years (25th-75th percentile, 38-55 years) and the median BMI was 46.3 (25th-75th percentile, 42.3-51.8) prior to surgery. Most participants were female (80.3%) and white (85.6%). The median follow-up was 6.6 years (25th-75th percentile, 5.9-7.0 years). The median percentage of maximum weight loss was 37.4% (25th-75th percentile, 31.6%-43.3%) of presurgery weight and occurred a median of 2.0 years after RYGB surgery (25th-75th percentile, 1.0-3.2 years). The rate of weight regain was highest during the first year after reaching nadir weight, but weight regain continued to increase throughout follow-up (range, a median of 9.5% of maximum weight lost [25th-75th percentile, 4.7%-17.2%] to 26.8% of maximum weight lost [25th-75th percentile, 16.7%-41.5%] 1 to 5 years after reaching nadir weight). The percentage of participants who regained weight depended on threshold (eg, 5 years after nadir weight, 43.6% regained ≥5 BMI points; 50.2% regained ≥15% of nadir weight; and 67.3% regained ≥20% of maximum weight lost). Compared with other continuous weight regain measures, the percentage