Virtually all body fat and glycogen are available for oxidation
, less than half the protein is available for oxidation. The size of the stores determines survival during starvation. Bodyweight depends on energy balance. Intake depends not only on food availability but also on a number of complex interrelationships that include the stimulus of good food, the role fo hunger, metabolic changes (e.g. hypoglycaemia), and the pleasure and habit of eating. Some people are able to keep their bodyweight constant within a few kilograms for many years, but most gradually increase their weight owing to a small but continuous increase of intake over expenditure. A gain or loss of energy of 25-29MJ (6000-7000 kcal) would respectively increase or decrease bodyweight by approximately 1kg.