Transcutaneous Auricular Vagus Nerve Stimulation Combined With Lifestyle Intervention for Visceral Fat Reduction in Adults With Overweight or Obesity

This is a single-center, randomized, open-label controlled trial with blinded outcome assessment and data analysis. Fifty adults with overweight or obesity (body mass index \[BMI\] \>= 24 kg/m2) and a sedentary lifestyle will be randomly assigned in a 1:1 ratio to one of two groups: (1) a transcutaneous auricular vagus nerve stimulation (taVNS) group, in which participants self-administer taVNS at the cymba conchae of both ears on alternating days (20 Hz, dense-disperse mode, twice daily, 30 minutes per session, 5 days per week for 4 weeks) in addition to a standardized lifestyle program; or (2) a control group receiving the lifestyle program alone. The lifestyle program prescribes a daily energy intake of 1,000-1,500 kcal (55-60% carbohydrate, 25-30% fat, 20% protein) plus aerobic exercise of at least 30 minutes per session, 3 times per week. The primary outcome is the change in visceral fat index (VFI) from baseline to week 4. Secondary outcomes include changes in body weight, BMI and body fat percentage, as well as changes in thalamocortical functional connectivity, effective (directed) connectivity, and whole-brain functional network topological properties assessed by resting-state functional magnetic resonance imaging (fMRI), and their associations with changes in obesity-related indicators. Assessments are performed at baseline (week 0) and after the 4-week intervention (week 4).

Inclusion Criteria: * Aged 18-49 years * Overweight or obesity, defined as BMI 24-32.5 kg/m2 according to Chinese criteria * Habitual sedentary lifestyle (less than 2 hours of daily walking and fewer than 3 exercise sessions per month on average over the past 6 months) * No metabolic diseases detected on routine physical examination * Right-handed Exclusion Criteria: * History of neurological or psychiatric disorders * Contraindications to MRI (e.g., metallic implants, orthodontic appliances or braces, claustrophobia) * Intracranial lesions * Prior use of hormonal medications * Current pregnancy or lactation