Introduction - Short sleep duration is a well-documented potential risk factor for obesity, one that is likely to affect vulnerable populations in particular. The primary objective of this study was to examine the association between short sleep duration and the risk of obesity among women receiving food assistance in France. Method - Total sleep time (TST) was measured using a sleep diary that allowed for precise differentiation between time spent in bed (TSB) and TST. The association between very short TST and the risk of obesity was analyzed using multivariate logistic regressions. Results - More than one in 10 women (11.6%) had particularly short sleep duration (TSD < 5 hours). The prevalence of obesity was very high among women with TSD < 5 hours: 55.6% versus 32.6% (p < 0.05) for those with TSD ≥ 5 hours. After adjusting for sociodemographic factors, sleeping less than 5 hours was significantly associated with the risk of obesity (measured body mass) among women.Conclusion - The association between short sleep duration and measured obesity identified in our analysis highlights the importance of comprehensive obesity prevention in vulnerable populations that incorporates sleep considerations. These results need to be confirmed by further studies conducted on similar populations. [author abstract]