Relationships between religion and body weight were examined in a US national sample.Data from the National Survey of Midlife Development in the United States (MIDUS), collected through telephone and postal questionnaires, were analyzed for 3032 adults aged 25-74.Religious denomination was significantly related to higher body weight in men after accounting for sociodemographic controls. Conservative Protestant men had a 1.1 +/- 0.45 higher body mass index (BMI) than those reporting no religious affiliation. Other religion variables that initially had significant relationships with greater body weight before adjusting for control variables became nonsignificant after smoking was controlled. No significant relationships between religion and body weight were present in women.Religious denomination was related to body weight in men. Other dimensions of religiosity showing a relationship with higher BMI appeared to be because of the lower rates of smoking among more religious individuals.