People can develop eating disorders due to excessive body image concerns. The primary objective of this study was to examine the relationship between attention to body shape, social physique anxiety, and personal characteristics in a sample of Brazilians. The secondary objective was to evaluate the correlation of the constructs with the participants’ body composition. First, 1795 individuals (70% female; Mage = 25.5 ± 6.6 years) completed the Attention to Body Shape Scale, the Social Physique Anxiety Scale, and a sociodemographic questionnaire. Then, 286 participants (58% female; Mage = 25.3 ± 5.7 years) underwent a bioimpedance exam to identify body composition. Structural equation modeling was used to estimate the relationship between the variables. The greater the attention to body shape, the greater the expectations of negative physical evaluation and the less comfort with physical presentation. Younger age, female gender, consumption of supplements/substances for body change, restrictive diets, physical inactivity, poor self-assessment of food quality, and overweight/obesity were related to negative body concerns. An expectation of negative physical evaluation was positively correlated with body fat and negatively with muscle mass. Comfort with physical presentation was negatively correlated with fat and positively with muscle. These results can support preventive strategies aimed at reducing eating disorders resulting from body image concerns.