Lactobacillus gasseri BNR17 is a probiotic strain isolated from human breast milk. Animal studies reported that BNR17 inhibited increases in body weight and adipose tissue weights. The purpose of this study was to evaluate the antiobesity effects of BNR17 in humans. In a randomized, double-blind, placebo-controlled trial, 90 volunteers aged 20-75 years with body mass index (BMI) from 25 to 35 kg/m² were randomized to receive a placebo, low-dose BNR (BNR-L, 10⁹ CFU/day), or high-dose BNR (BNR-H, 10¹⁰ CFU/day) for 12 weeks. Body weight, BMI, waist and hip circumferences, waist-to-hip ratio, abdominal adipose tissue areas, body fat mass, lean body mass, and biochemical parameters were assessed at the beginning and end of the trial. Visceral adipose tissue (VAT) was significantly decreased in the BNR-H group compared with the placebo group (P = .038). Difference of VAT areas of the BNR-H group compared with the placebo group after 12-week consumption of BNR17 was significant (-21.6 cm², P = .012). Waist circumferences were significantly decreased in both the BNR-L and BNL-H groups (P = .045 and .012, respectively) compared with the baseline values, but not in the placebo group. Biochemical parameters were not significantly different among the groups. These findings suggest that daily consumption of BNR17 may contribute to reduced visceral fat mass in obese adults.