Our population is ageing, and obesity is increasing in the elderly bringing massive and rapidly changing burdens of ill health related to increased body weights and fat as well as the main drivers of poor diet and inactivity. Overweight and obesity, and a static body mass index (BMI) commonly conceal sarcopenia (gain in body fat but loss of muscle mass and functional capacity) in older people, aggravated by inactivity. A systematic computerized literature search using an iterative manipulation process of the keywords: obesity, elderly, weight loss. The following databases were accessed on 20 October 2010: Medline, Cochrane Collaboration, Ovid and Scholar Google. A large number of clinical consequences of overweight and obesity are particularly problematic for elderly individuals, including type 2 diabetes mellitus, arthritis, urinary incontinence and depression. The observation that the BMI value associated with the lowest relative mortality is slightly higher in older than in younger adults has often been misinterpreted that obesity is not as harmful in the elderly. BMI may be a less appropriate index in the elderly. All the medical consequences of obesity are multi-factorial but all are alleviated by modest, achievable weight loss (5-10 kg) with an evidence-based maintenance strategy. Since sarcopenic obesity is common in the elderly, a combination of exercise and modest calorie restriction appears to be the optimal method of reducing fat mass and preserving muscle mass. Reduction in polypharmacy is a valuable target for weight management. Age is not an obstacle to weight management interventions using moderate calorie restriction and exercise, and the currently licensed drug orlistat appears to have no age-related hazards. Overall balance of clinical outcomes has not been evaluated. In older people the risks from bariatric surgery outweigh benefits. Obesity, and specifically sarcopenic obesity, should also be prevented not only from younger age, but also during major life transitions including retirement, to improve better health outcomes and quality of life in later years, with a focus on those in 'obese families', where the main increases in obesity are located. Randomized controlled trials to determine health benefits and risks from long-term weight management in obese elderly are necessary.