A common assumption in models of insecticide resistance evolution is the association between resistance and fitness cost. There are empirical evidences of such association, but their physiological basis (and mitigation) was seldom investigated. Pyrethroid resistant populations of the maize weevil (Sitophilus zeamais (Coleoptera: Curculionidae)) offer this opportunity. Pyrethroid resistance in this species was initially observed in five Brazilian states, but the phenomenon apparently decreased and did not spread to other regions probably due to the occurrence of fitness disadvantage in resistant individuals in the absence of insecticides. The present investigation tried to verify if differences in respiration rate and fat body morphology are related with differences in rate of development in Brazilian populations of S. zeamais resistant to insecticides providing evidence of the existence (or not) of physiological cost determining fitness cost of insecticide resistance in populations of this insect-pest. To achieve this, studies of rate of development, respiration rate and fat body cytomorphology were carried out in one insecticide susceptible (from Sete Lagoas) and two resistant populations (from Jacarezinho and Juiz de Fora) of S. zeamais. The resistant population from Jacarezinho shows higher body mass incurring in more stored energy (higher trophocyte area) resulting in enough energy reserves not only for its development and reproduction, but also for insecticide resistance. The resistant population from Juiz de Fora however, does not seem to have large enough energy reserves for insecticide resistance expression and development and/or reproductive performance leading to a trade-off between resistance and other fitness-related traits.