Traditional diet and exercise treatments for obesity have been ineffective in reducing the prevalence of overweight in the population. Treatment outcomes for overweight can be measured in terms of physical parameters (e.g. bodyweight, percentage body fat, body mass index), medical terms (e.g. blood pressure, blood glucose control, blood lipid levels), psychological terms (e.g. eating pathology, self-esteem, mood state) and behavioural terms (e.g. frequency of exercise, eating patterns, self healthcare). Regardless of the specific outcome measures used to define successful treatment, the desired outcome must be maintained for several years to be considered effective. Energy restrictive diets cause significant initial bodyweight loss, but are plagued with high dropout- and relapse-rate. Low-fat diets have met with minimal success for bodyweight control, but nonetheless can significantly lower blood lipid levels. High-protein/low-carbohydrate diets are claimed to be the most effective in reducing bodyweight, but there are no scientific data to support these claims. Persons on these types of diets are also at the greatest risk for metabolic adverse effects. Nondieting approaches and programmes that stress ‘health at any size’ have not been researched rigorously, but preliminary data show minimal bodyweight loss with significant improvements in psychological state, eating pathology and well-being. Exercise is the only variable that consistently shows effectiveness in physiological, medical, psychological and behavioural outcomes. A treatment programme that has the greatest potential for success, regardless of outcome measure, is a programme that consists of 4 key components. These components are:pre-evaluation, where historical information is gathered and used to set programme goals, objectives and outcome measures;exercise, wherein enjoyable exercise is encouraged for health, bodyweight control and well being;a behavioural plan, which is based on patterns of eating and activity that will lead to the desired outcome measures; anda maintenance plan, that helps the individual develop skills for maintaining newly developed behaviours.