Bariatric surgery (BS) is known to improve the components of metabolic syndrome (MS) in obese patients. However, few studies have evaluated the impact of bariatric surgery versus medical therapy (MT) in patients with MS, especially in patients with low body mass index (BMI). This study aimed to assess the effect of bariatric surgery on MS in patients with low BMI by comparing BS (BMI<35 kg/m2 and BMI≥35 kg/m2) with MT (BMI<35 kg/m2). A retrospective study including patients with MS undergoing bariatric surgery and medical therapy at a single institution. We follow up the 5 years effect of bariatric surgery versus medical therapy on the remission of MS, its individual components, atherosclerotic cardiovascular disease (ASCVD) risk, and medication used.

1. Study design and patients

   This study aimed to compare bariatric surgery(BS) with medical therapy (MT) for the management of low BMI patients with MS, approved by the ethics committee and institutional review at our hospital. 100 patients underwent bariatric surgery and 100 patients receiving medical therapy for obesity and type 2 diabetes between 2010 and 2020 at our institution. All patients met the Chinese guidelines developed by the Chinese Society for Metabolic & Bariatric surgery (CSMBS). All patients achieve diagnostic criteria for MS, defined by the presence of at least 3 of the 5 following criteria derived from the joint interim statement (JIS) definition.

2. outcome and Data collection

   All patients follow up the change of improvement in MS and its components following bariatric surgery and medical therapy, including waist circumference, hyperglycemia, hypertension, hyperlipidemia, long-term CVD risk, and medication use

3. Treatments

3.1 BS group The bariatric surgical procedures performed included Roux-en-Y gastric bypass and sleeve gastrectomy.

3.2 MT group According to the guidelines in China, patients in the medical therapy group received glucose-lowering, lipid-lowering, and antihypertensive medications, with the following targets: glycosylated hemoglobin<7%; systolic blood pressure<140 mmHg, diastolic blood pressure<80 mmHg; low-density lipoprotein cholesterol<2.6 mmol/L; and high-density lipoprotein cholesterol>1.3 mmol/L for female or 1.0 mmol/L for male.

1. Inclusion Criteria:

   • BMI<35 kg/m^2
   • Underwent bariatric surgery or medical therapy
   • Patients met the diagnostic criteria for MS, defined criteria derived from the joint interim statement (JIS)

2. Exclusion Criteria:

   • Patients who failed to follow up
   • Insulin dependent diabetes
   • congenital dementia
   • brain trauma
   • epileps
   • severe hypoglycemic coma
   • cerebrovascular disease
   • ischemic
   • heart disease
   • renal dysfunction
   • alcohol abuse
   • mental illness
   • psychoactive substance abuse
   • unwillingness to provide informed consent

Patients underwent bariatric surgery or medical therapy for metabolic syndrome between 2010 and 2020 at our institution.