Effects of bariatric surgery in different obesity phenotypes: Tehran Obesity Treatment Study (TOTS)

Background Not all morbid obese patients suffer from metabolic co-morbidities; thus, a sub-group of metabolically healthy morbid obese (MHMO) individuals are identified. However, the role of bariatric surgery is not well understood in this subgroup. Methods A total of 2244 morbid obese individuals aged 18–65 years undergoing bariatric surgery were selected. Patients were considered MHMO according to the joint interim statement (JIS) definition, as having two or less abnormalities in these five parameters: waist circumference (WC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), systolic or diastolic blood pressure (SBP or DBP), and fasting plasma glucose (FPG). Otherwise, they were considered metabolically unhealthy morbid obese (MUMO). Follow-up data were collected at 6, 12, and 24 months post-surgery. Results Prior to surgery, 36.2% of participants were MHMO and had significantly lower BMI, WC, TG, FPG, SBP, and DBP and higher HDL-C compared to MUMO. Both MHMO and MUMO participants showed a significant decrease in BMI, WC, TG, SBP, DBP, and FPG and increase in HDL-C and the percentage of excess weight loss (%EWL). Two-year post-operative changes (from baseline) of BMI, WC, and %EWL were greater in MHMO subjects and changes of TG, HDL-C, DBP, SBP, and FPG were greater in MUMO subjects. Further multivariate regression analysis for delta (∆) change in these characteristics revealed that only the delta (∆) changes of WC and %EWL were statistically different between the two phenotypes and were greater in MHMO subjects, 2 years after the surgery (− 3.077 cm decrease in WC and + 3.612% higher %EWL compared to MUMO subjects). Conclusion Bariatric surgery is an effective method for reduction of metabolic abnormalities and weight loss in both MUMO and MHMO phenotypes. Benefits of this intervention are comparable between patients with these two obesity phenotypes.