We use time-series of rainfall to estimate the response of body weight to transitory changes in household income in rural Tanzania. We find that the response of body weight to income changes is positive on average, but that the impact is highest for female children, and lower for adults. For female children, a ten-percent increase in household income implies an increase in body weight by about 0.4 kg. In contrast, the body weight of adolescents and young adults is virtually invariant to income changes.