Helicobacter pylori (H. pylori) infection can induce chronic inflammation and is associated with insulin resistance, metabolic syndrome and body mass index (BMI, kg/m2) changes. This study aimed to evaluate the association between H. pylori infection and overweight/obesity. This research was a cross-sectional study conducted from March 2014 to November 2016, using data from the three districts in the northeastern region of Taiwan. The inclusion criteria were an age >30 years and the absence of pregnancy. Ultimately, 2686 subjects (1713 women) were included in this study. Among the subjects aged less than 50 years, the subjects with H. pylori infection had higher mean BMI values than those without H. pylori infection (40-49 years: 25.7 ± 4.4 vs. 24.7 ± 3.8, P = 0.025; 30-39 years: 24.9 ± 4.4 vs. 24.0 ± 4.1, P = 0.063). H. pylori infection increased the risk of being obese 2 (BMI ≥30) (odds ratio, OR = 1.836, 95% CI = 1.079-3.125, P = 0.025) with adjustments for demographic factors in subjects aged less than 50 years. In conclusions, subjects with H. pylori infection and age less than 50 years may increase a risk of being obesity (BMI ≥30) compared to those without this type of infection.