Many claims about nutrition and weight loss stem from small, short-term studies, incorrect interpretations or distortions of evidence. Our knowledge of what people eat is poor; difficulties include accurate assessment of consumption, the complex composition of foods and individual variations in nutrient bioavailability. When advice appears to be ineffective, poor compliance is a likely explanation. There is no simple solution to obesity, and no fast way to create the energy deficit required for sustainable loss of fat - weight loss requires long-term commitment to permanently change eating and exercise habits. Valid advice is to reduce overall energy intake, include more vegetables, fruits and whole grain products and fewer foods high in saturated fat, sugar and salt. While mindful of the need to encourage individuals to make changes, the medical profession needs to lead the charge to advocate for changes to our obesogenic environment.