Obesity is an issue that is increasingly affecting ageing men. With ageing, there is a decline in androgens as well. There are implications for the health of ageing men as a result of hypogonadism. Overall, there seems to be an inverse relationship between body mass index and testosterone levels, as is also demonstrated in our cross-sectional study. Obesity seems to depress the production of testosterone. It has been hypothesized that there is increased aromatization of testosterone to oestradiol and alteration of the hypothalamic-pituitary-adrenal axis in obese older men. Some hormones can affect obesity in ageing men including leptin, insulin, dehydroepiandrostenedione and growth hormone. The relationship of obesity to these hormones in ageing men will be reviewed. Testosterone replacement in ageing men can alter body composition whereby fat is exchanged for muscle. These studies will also be reviewed. Further studies in this field are recommended to evaluate long-term benefits and risks.