Weight Regain Post Bariatric Surgery

This study aims to compare the effects of time-restricted eating (TRE, 16/8) in adults with obesity who have and have not undergone bariatric surgery (BS). The study will include adults aged 18-65 years: those with obesity who have not undergone BS, and those who have experienced insufficient weight loss (IWL) or weight regain (WR) following BS. Both groups will follow a 16:8 time-restricted eating protocol for 6 weeks, with an 8-hour eating window recommended between 10:00 AM and 6:00 PM, though participants may adjust to other 16-hour fasting windows. Participants will be evaluated before and after the intervention in terms of anthropometric measurements, biochemical parameters, and dietary habits. The study is being conducted at a private hospital in Bursa, Turkey, and is planned to be completed with a total of 40 participants (20 per group).

The goal of this clinical trial is to evaluate the superiority of combined VLCKD, intensive lifestyle intervention and naltrexone/bupropion (N/B) versus standard of care with naltrexone/bupropion on weight loss for people with weight regain after bariatric surgery. The main questions it aims to answer are: Primary endpoint: • The percentage of weight loss at 26 weeks Secondary endpoints: * A weight loss percentage at 10 weeks, 16 weeks and at end of trial (= 52 weeks from start) * A proportion of patients with a weight loss percentage of 5% or more at 10, 16, 26 and 52 weeks * A proportion of patients with a weight loss percentage of 10% or more at 10, 16, 26 and 52 weeks * The time to reach a weight loss percentage of 5% and 10% * The dose of naltrexone/bupropion used at 10, 16, 26 and 52 weeks and at the end of the trial * The tolerability of VLCKD and NB * The adherence to VLCKD and NB * The Patient-Reported Outcome Measures (PROMs) of hunger and cravings at 0, 4, 10, 16, 26 and 52 weeks * The change in fasting glucose, lipids and blood pressure at 10, 16, 26 and 52 weeks Researchers will compare an experimental arm (N/B + Lifestyle + VLCKD) with comparator arm (NB + lifestyle) to see if combined VLCKD, intensive lifestyle and N/B is superior. Participants will: * get NB and lifestyle changes for 26 weeks * follow a VLCKD in the first 10 weeks on top of it, if they belong to the experimental arm * follow NB combined with lifestyle the remaining 16 weeks * be followed-up for an extension of 26 weeks * come to the hospital at week 1, 10, 16, 26, 52