© 2018, Springer Nature Limited. The objective of this review is to highlight changes in body composition in rodent models as a result of healthy aging in order to enhance translational research. Aging is associated with alterations in body composition, particularly fat mass and fat-free mass, which may be accompanied by adverse health effects, especially nearing middle age to old age. In humans, it is generally understood that fat mass tends to increase while fat-free mass concurrently declines with aging. However, the effect of aging on body composition in rodent models is less well studied, and how these changes compare and contrast with observations in humans has not yet been fully elucidated. Though, it appears as though the constituent-level alterations occur in humans and rodents at different life phases thereby having a potential effect on the outcomes of basic biomedical research. Though highly strain-dependent, this review suggests that FM changes begin at a much earlier life phase in rodents than in humans. Conversely, FFM appears to increase throughout middle age and into old age in rodents, whereas middle age is associated with the initiation the subsequent decline of FFM in humans. Given the essentiality of rodent models in basic biomedical research, careful consideration of these differences in age-related BC findings is imperative when the research is aimed for human translation.