OBJECTIVES: The purpose of this review was to describe the characteristics of late-life obesity, including prevalence, pathophysiology, and influences on morbidity and mortality. A second objective was to systematically review the empiric evidence on the effects of intentional weight loss interventions in older individuals. DESIGN: We summarized the characteristics and known impact of late-life obesity and conducted a systematic review of the outcomes of weight loss interventions in obese older subjects. The inclusion criteria for the review were the following: randomized controlled trial; subjects aged 60 years or older; baseline BMI 27 or higher; weight loss versus baseline 3% or more or 2 kg; and trial duration 6 months or longer. RESULTS: The search strategy yielded 16 articles on weight loss interventions that were examined in detail. Overall, these interventions led to significant benefits for those with osteoarthritis, coronary heart disease, and type 2 diabetes mellitus (DM-2), while having slightly negative effects on bone mineral density and lean body mass. CONCLUSION: Longitudinal trials examining mortality and body weight suggest that maintaining weight is beneficial in older persons who become obese after age 65; in contrast, intervention trials show clinically important benefits of weight reduction with regard to osteoarthritis, physical function, and possibly DM-2 and coronary heart disease. Given these findings, we recommend that decisions about whether or not to institute a weight loss intervention for obese older persons be carefully considered on an individualized basis with special attention to the weight history and the medical conditions of each individual.