Short-term studies indicate that intentional weight loss (IWL) among obese persons significantly improves health variables that are often precursors or markers of chronic diseases (e.g. heart diseases, type-2 diabetes). Hence, it is logical to assume that IWL among obese persons would lead to increased longevity. On the whole, epidemiological studies, including recent ones that use conservative analytic approaches such as distinguishing between apparently IWL and unintentional weight loss (UWL), adjusting for potential confounders and excluding apparently unhealthy subjects, indicate that apparently IWL appears to neither increase nor decrease mortality rate. However, it is important to note that none of the existing studies were designed specifically to test the hypothesis that IWL reduces mortality rate, and given methodological problems, these studies do not provide a satisfactory way to address the body mass index (BMI)-mortality question. Several controlled clinical trials suggest that IWL may reduce mortality rate. However, even in these studies, it is important to acknowledge that subjects are randomized to conditions that produce more or less weight loss and not to distinct levels of weight loss per se. Nevertheless, while we await additional data from better designed studies, given our incomplete knowledge, we conclude that it seems more likely than not that IWL achieved by medically recommended methods does not increase and probably decreases mortality rate.