Comparing effects of obesity treatment with very low energy diet and bariatric surgery after 2 years: a prospective cohort study

OBJECTIVES: To compare long-term effects and complications of medical treatment (MT) of obesity including very low energy diet with bariatric surgery. DESIGN AND SETTING: This prospective study conducted in a clinical setting recruited individuals with body mass index (BMI) ≥35 kg/m(2) referred for obesity treatment. Demographic and anthropometric data, laboratory samples, and questionnaire replies were collected at baseline and 2 years. PARTICIPANTS AND INTERVENTIONS: 971 individuals were recruited 2015–2017. 382 received MT, 388 Roux-en-Y gastric bypass (RYGB) and 201 sleeve gastrectomy (SG). MAIN OUTCOME MEASURES: Primary outcomes included changes in anthropometric measures, metabolic variables and safety. These were analysed using a linear regression model. A logistic regression model was used to analyse composite variables for treatment success (secondary outcomes). A random forest (RF) model was used to examine the importance of 15 clinical domains as predictors for successful treatment. RESULTS: Two-year data were available for 667 individuals (68.7%). Regarding primary outcomes, the decrease in excess BMI was 27.5%, 82.5% and 70.3% and proportion achieving a weight of >10% was 45.3%, 99.6% and 95.6% for MT, RYGB and SG, respectively (p<0.001). The groups were comparable regarding levels of vitamins, minerals and haemoglobin or safety measures. Likelihood for success (secondary outcome) was higher in the surgical groups (RYGB: OR 5.3 (95% CI 3.9 to 7.2) vs SG: OR 4.3 ((95% CI 3.0 to 6.2)) in reference to MT. Baseline anthropometry had the strongest predictive value for treatment success, according to the RF model. CONCLUSIONS: In clinical practice, bariatric surgery by RYGB or SG is most effective, but meaningful weight loss is achievable by MT with strict caloric restriction and stepwise introduction of a normal diet. All treatments showed positive effects on well-being, cardiovascular risk factors, and levels of vitamins and minerals at 2-year follow-up and groups were similar regarding safety measures. TRIAL REGISTRATION NUMBER: NCT03152617.