Obesity is a growing problem. In England in 2008, 66% of men and 57% of women had a BMI >25 kg/m2; within this 24% of men and 25% of women were obese with a BMI >30 kg/m2. Obesity is a major contributing cause of disease. The relative risk (RR) of diabetes in overweight men is 2.40 and in obese men 6.74 compared with men with a BMI in the normal range. The respective RR values in women are 3.92 and 12.41. There is a 40% increased risk of death from CVD for every 5 kg/m2 increase in BMI above 25 kg/m2. Obesity is also associated with a raised risk of: fertility problems, cirrhosis, osteoarthritis, pregnancy complications, obstructive sleep apnoea and asthma. Patients should be offered advice on dietary change and increasing physical activity which includes behavioural components. Encouragement to make small changes in a sustained way can make significant differences to energy balance. Physical activity should be of moderate intensity (increased heart rate and breathing but still able to converse). Drug treatment is a useful addition when lifestyle measures alone are not effective. Evidence is increasing for the effectiveness of bariatric surgery in treating obesity-related disease, particularly diabetes.