The body maintains energy balance throughout the daily feed-fast cycles, across periods where energy demands increase due to physical exertion, and when energy supplies are depleted due to nutrient deprivation. During a typical day, several meals are consumed leading to periods of time several hours long after the meals, the fed state, where there is a net energy gain. This situation changes during sleep and during gaps in meal intake where the net energy balance, that is calories in minus calories out, becomes negative. These are the fast states that lead to refeeding. The ability of the body to maintain energy balance is centered about a set of peripheral organs and tissues that digest, convert, ship, and store nutrients and energy, namely,
In the fed state, nutrients – carbohydrates, fat, and amino acids – are taken in, converted, and stored. In response to the increase in circulating glucose, the pancreas secretes insulin...