PURPOSE: Thyroid nodularity has been associated with obesity, but data regarding associations of body composition parameters with specific ultrasound features of thyroid nodules are lacking. The aim of the present study was to assess associations between thyroid nodule ultrasound characteristics, lifestyle, and anthropometric parameters.SUBJECTS AND METHODS: This was a cross-sectional study in the general apparently healthy population of Northern Greece. Thyroid ultrasound data together with medical history, demographic, and anthropometric characteristics were individually recorded. Body composition was evaluated using bioelectrical impedance.RESULTS: Three hundred and six subjects [215 females (70.3%), aged 20-83 years] were included. Ultrasound revealed one or more thyroid nodules in 168 subjects (54.9%). Subjects with thyroid nodules were more frequently females (p = 0.033), older (p < 0.001) and had higher fat mass (p = 0.011), total body fat percentage (p < 0.001) and waist circumference (p = 0.045) than subjects without nodules. In logistic regression analyses, age and female gender were the only independent predictors of presence of thyroid nodules, as well as specific sonographic features. Additionally, total body fat percentage was positively correlated with nodule size (rho = 0.210, p = 0.006) and was the only independent predictor of hypoechoic thyroid nodule(s) and peripheral vascularity, while lack of exercise was predictive of internal vascularity.CONCLUSIONS: Body fat accumulation and lack of exercise, used as surrogate markers of sedentary lifestyle, influence thyroid nodule size and could predict some ultrasonographic characteristics, like hypoechoicity and internal vascularity. Therefore, routine thyroid examination of obese patients and promotion of active lifestyle may be warranted to prevent thyroid nodule formation and possibly progression to malignancy.