Weight loss during medical weight management does not predict weight loss after bariatric surgery: a retrospective cohort study

Background: Many bariatric surgical centers mandate achieving weight loss targets through medical weight management (MWM) programs before offering bariatric surgery, but the evidence for this is unclear.

Objectives: To examine the relationship between weight changes during (1) MWM, and (2) preoperative low-energy-diet (LED), and weight changes at 12 and 24 months after surgery.

Setting: Multicenter community- and acute-based MWM services referring to one regional bariatric center, United Kingdom.

Methods: A retrospective cohort study of patients who attended MWM and then underwent a primary laparoscopic bariatric procedure (adjustable gastric banding [LAGB], or Roux-en-Y gastric bypass [RYGB]) in a single bariatric center in the United Kingdom between 2013 and 2015. Data were collected from patient electronic records.

Results: Two hundred eight patients were included (LAGB n = 128, RYGB n = 80). Anthropometric data were available for 94.7% and 88.0% of participants at 12 and 24 months, respectively. There was no relationship between weight loss during MWM and after surgery at either 12 or 24 months. Weight loss during the preoperative LED predicted greater weight loss after LAGB (β = .251, P = .006) and less weight loss after RYGB (β = -.390, P = .003) at 24 months, after adjusting for age, sex, ethnicity, baseline weight, and LED duration.

Conclusions: Weight loss in MWM does not predict greater weight loss outcomes up to 24 months after LAGB or RYGB. Greater weight loss during the preoperative LED predicted greater weight loss after LAGB and less weight loss after RYGB. Our results suggest that patients should not be denied bariatric surgery because of not achieving weight loss in MWM. Weight loss responses to preoperative LEDs as a predictor of postsurgical weight loss requires further investigation.