King WC, et al. - In this prospective cohort study, researchers characterized weight regain after reaching nadir weight following Roux-en-Y gastric bypass (RYGB) surgery, and compared weight regain measures for association with outcomes. They found that weight regains, quantified as a percentage of maximum weight lost, performed better for association with most clinical outcomes vs the alternatives examined among a large cohort of adults who had RYGB surgery. In studies of bariatric surgery, these outcomes might inform standardizing the measurement of weight regain.

Methods

• Study participants included 2,458 adults who had bariatric surgery at 10 hospitals in 6 US cities between March 2006 and April 2009.
• The investigators conducted assessments within 30 days’ pre-surgery, at 6 months post-surgery, and then annually until January 2015.
• Of 1,703 study participants who had RYGB surgery, 1,406 (83%) were followed up for ≥ 5 years and ≥ 5 weight measurements (excluding those who died or underwent surgical reversal).
• Based on statistical significance, magnitude of association, and model fit, weight regain assessed by five continuous measures—weight in kilograms, body mass index (BMI), percentage of pre-surgery weight, percentage of nadir weight, and percentage of maximum weight lost—and eight dichotomous measures (per established thresholds) were compared in relation to clinical outcomes.
• Main outcomes and measures analyzed were progression of diabetes, hyperlipidemia, and hypertension as well as declines in physical and mental health-related quality of life and satisfaction with surgery.

Results

• Among the participants who had RYGB surgery (n=1,406), median participant age was 47 years, and the median BMI was 46.3 prior to surgery.
• Most participants were female (80.3%) and white (85.6%).
• Median follow-up was 6.6 years.
• Median percentage of maximum weight loss was 37.4% of pre-surgery weight and occurred a median of 2.0 years following RYGB surgery.
• Findings revealed that the rate of weight regain was highest during the first year after reaching nadir weight; however, weight regain continued to increase throughout follow-up.
• Results indicated that 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).
• The percentage of maximum weight lost had the strongest association and best model fit for all outcomes except hyperlipidemia, which had a slightly stronger association with BMI vs other continuous weight regain measures.
• Data reported that ≥ 20% of maximum weight lost performed better or similarly with most of the outcomes, and was the second best measure for hyperlipidemia (after ≥ 10 kg of weight) and hypertension (after ≥ 10% of maximum weight lost) of the dichotomous measures.