TITLE PAGE Title: Lean Mass Predicts Asthma Better than Fat Mass among Women

The obesity phenotype associated with asthma is not known. Our objective was to define the relative contribution of various distributions of fat and lean mass to asthma prevalence. Data were obtained from 2,525 participants (including 1,422 women) who underwent Dualenergy X-ray Absorptiometry (DEXA) at the year 20 examination in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort. Total, truncal, arm, and leg distributions of fat and lean mass were adjusted to the person’s height. Self-reported asthma was the outcome. Asthma among women was associated with greater total fat mass, arm fat mass, and total lean mass, truncal lean mass, and arm lean mass. Among men, none of the above mass measures were significantly associated with asthma. Among women, the association with asthma was stronger for total lean mass than for total fat mass. Further, among various regional distributions of lean and fat mass in women, truncal lean mass was the strongest predictor. Total lean mass is more strongly associated than total fat mass with asthma among women. These findings are contrary to the popular perception that excess physiological fat drives the obesity-asthma association. Rather, we hypothesize that ectopic fat within the ‘lean’ tissues drives this association among women.