Weight loss is theoretically simple: decrease energy intake, increase energy use, or both. As millions of 'yo-yo' dieters can attest, translating this into practice is far from simple.This review will explore the issues surrounding the low fat approach to weight loss and suggest sensible and alternative recommendations for patients.Although short term weight loss can be achieved by many diets, sustained behaviour change and long term weight maintenance is far more difficult. Hence the essence of any weight intervention is a change in diet and activity that is sustainable in the long term; to achieve this means encouraging patients to make appropriate lifestyle changes.