Adiposity over the life course and prostate cancer: unraveling the complexities.

The association between obesity and prostate cancer has been extensively studied, but clear answers have evaded us. Most of the studies have been based on a single time-point measure, most commonly of body mass index (BMI) during adulthood. Emerging data suggest a complex pattern that may be better understood through a life course approach. The data suggest that early life adiposity, possibly before or during puberty, as being associated with lower risk of advanced prostate cancer. In contrast, moderate weight gain in men who were initially lean during pre-adulthood or early adulthood may increase risk of advanced prostate cancer. This pattern suggests competing factors associated with overall adiposity, some protective and some adverse. Factors that may increase risk appear to show more strongly in men who maintain a relatively low BMI but have a high waist circumference or waist:hip ratio. Possibly, this pattern may be associated with relatively high levels of factors associated with insulin resistance and related metabolic abnormalities (mostly central adiposity) while avoiding the protective factors (mostly generalized or subcutaneous adiposity). Broad measures at one time-point, such as adult BMI, are not likely to contribute further to our understanding. Instead, direct measures of visceral fat might be useful. For feasibility, combined measures, such as examining waist:hip ratio among men with normal BMI in relation to risk, might be useful. It may be informative to better determine the precise point in early life when adiposity may be protective and through what mechanisms, such as delay in puberty.