Several studies indicate that women are more likely than men to exercise for appearancerelated reasons, but today, even men have become more concerned about how they look. Exercise and/or diets are sometimes used in an attempt to develop a more attractive physique. Strict diets such as an obsession with healthy food, sometimes termed orthorexia nervosa (ON), are controversial and have been questioned by researchers. This study investigates how scores on the Social Physique Anxiety Scale (SPAS) and the Sociocultural Attitudes Towards Appearance Questionnaire (SATAQ) relate to Bratman’s orthorexia test (BOT) scores with regard to age, sex, and self-reported exercise frequency and duration. The fitness participants (n=251, 166 women and 85 men, 21% dropout) were consecutively selected from five fitness centers in Sweden. They completed the BOT, SPAS, SATAQ, and a questionnaire focusing on exercise frequency and duration. Multiple stepwise regression analysis was used and the significance level set at 5%. In men, the results indicated that the SATAQ subdomain internalization could itself explain the variation in BOT results. In women, the results demonstrated that exercise frequency, in combination with the SPAS score and the SATAQ subdomains of internalization and awareness, could explain the variation in BOT results. Internalization of a slimness ideal (for women) and a muscular body (for men) can be a risk factor for obsession with diet. In the same way, higher exercise frequency, a higher level of social physique anxiety and awareness of Western body ideals seem to be predictors of obsession with diet among women. It is possible that the fitness center environment emphasizes a body ideal that leads to an increased obsession with diet. On the other hand, it may be that people who are aware of the body ideal and are obsessed with diet are the ones who engage in fitness center activities.