2.3 Post absorptive signals

Fluctuations in blood glucose level affect appetite. Low blood glucose level (hypoglycaemia) stimulate hunger. There is a homeostatic balance of blood glucose level. As blood glucose increases, a hormone – insulin – is secreted by the pancreas. This is an acute appetite suppressant.

You may have heard of leptin which is released by adipose tissue (fat cells) in the body. This decreases during a period of fasting and increases when you eat. Leptin acts on the hypothalamus in the brain, which causes the release of neuropeptides (e.g. neuropeptide Y), which inhibits food intake.

Another neuropeptide called orexin (hypocretin) is involved with arousal, wakefulness and appetite. This increases the craving for food. Leptin inhibits craving, while ghrelin and hypoglycaemia stimulate orexin-producing cells in the hypothalamus and spinal cord.

So, the next time you crave something to eat, blame it on your orexin!