Calorie restriction increases longevity in rodents, delays the onset of certain diseases and has positive effects on ageing. Studies are ongoing in non-human primates. Eight persons following such a diet for 2 years reacted as anticipated (loss of body weight and fat, decrease in glycaemia and body temperature, etc.). Calorie restriction perhaps teaches us more on the means of resisting malnutrition than on ageing in normal dietary conditions. Calorie restriction is a tool for research, but it should not be recommended by practitioners, notably in elderly patients.