Food deserts are increasingly considered as a potential cause of overweight and obesity, yet existing literature is largely inconclusive in part due to the infeasibility of sorting out multiple confounding mechanisms from a purely empirical perspective. This article investigates the hypothesized causality in a rational-choice framework, where the individual chooses how much to patronize a distant supermarket and/or a nearby convenience store, broadly defined, and the weight outcome depends on this choice. Results suggest that neither limited supermarket access nor low income, the key features of food deserts, would determine the weight outcome, which is also affected by individual preferences as well as time and monetary costs associated with grocery shopping. Parametric conditions under which varying effects on weight occur are further derived to elicit policy implications