Obesity management includes primary weight loss, prevention of weight regain, and the management of associated risk factors, such as smoking, hyperlipidaemia and hypertension. All these require lifestyle modification. The success or failure of management will depend on the characteristics of both the patient and the physician (or therapeutic team). Thus, direct statistical comparisons between methods of management may be misleading. Weight loss of 5-10% (usually 5-10 kg and equivalent to 5-10 cm waist reduction for most patients) is generally achievable within 3-4 months. Attempts to achieve weight loss over longer periods of time are usually unsuccessful. Improved clinical, symptomatic and biochemical benefits are very significant with this degree of weight loss. It is therefore unreasonable to pursue an 'ideal' bodyweight. In reported studies, the weight decrease over the first 3-4 months represents the total weight loss. Data collected after this time reflect both the initial weight loss and the ability of the patient and the programme to maintain weight loss. Many reports and study designs do not make this distinction. The principal goal of weight management, whether in primary prevention or in treatment of the obese, is weight maintenance. This goal has to be viewed in the context of a normal tendency to gain weight through adult life. In good hands, dietary and behavioural techniques can maintain significant weight loss for 1 year or longer in about 40% of patients. This increases to about 70% for patients receiving appetite modifying drugs; professional resource requirements are also lower. Surgical approaches are reserved for those with more serious clinical risks. Weight loss in individuals with non-insulin dependent diabetes mellitus (NIDDM) can be achieved in newly diagnosed patients and non-diabetics with comparable success. The goal of interventions in established NIDDM patients should be improved weight maintenance evaluated over 1-2 years, not acute loss achieved in 3 months.