Psychosocial stress has been strongly implicated in the biology of adiposity but epidemiological studies have produced inconsistent results. The aim of this analysis was to bring together results from published, longitudinal, prospective studies examining associations between psychosocial stress and objectively measured adiposity in a meta-analysis. Searches were conducted on Medline, PsycINFO, Web of Science, and PubMed (to January 2009) and reference lists from relevant articles were examined. Prospective studies relating psychosocial stress (general life stress (including caregiver stress), work stress) to BMI, body fat, body weight, waist circumference, or waist-to-hip ratio were included. Analyses from 14 cohorts were collated and evaluated. There was no significant heterogeneity, no evidence of publication bias, and no association between study quality and outcomes. The majority of analyses found no significant relationship between stress and adiposity (69%), but among those with significant effects, more found positive than negative associations (25 vs. 6%). Combining results in a meta-analysis showed that stress was associated with increasing adiposity (r = 0.014; confidence interval (CI) = 0.002-0.025, P < 0.05). Effects were stronger for men than women, in analyses with longer rather than shorter follow-ups, and in better quality studies. We conclude that psychosocial stress is a risk factor for weight gain but effects are very small. Variability across studies indicates there are moderating variables to be elucidated.