Economic approaches to nutrition have focused largely on measures of child nutrition and thus have been able to ignore the issue of individual heterogeneity in energy expenditures. Ignoring such an issue may be bad science, however, especially given the case of adults, whose waking hours are devoted mostly to labor activities, the energy costs of which vary enormously. An instrumental variables technique was employed to obtain consistent estimates of the structural parameters of the nutrition production function for adult women in Ghana. Energy expenditure, as embodied in individual time allocations over the previous seven days, was found to be an important determinant of female nutritional status, with time devoted to agricultural tasks, in particular, having a strong negative effect. Perhaps most importantly, evidence was found of a substantial downward bias of the calorie elasticity estimate when the energy expenditure proxies were excluded.