How does a lack of sleep impact our appetite? Have you ever noticed that after a late night out or generally just not getting enough sleep, the next day you are hungrier? This can be explained by the impact sleep deprivation has on metabolic hormones.
When we eat and glucose enters the bloodstream, insulin is released from the pancreas in order to instigate the movement of the glucose into the cells to be used for energy. Insulin locks into insulin receptors on the cell surface – this is a lock and key mechanism – think of insulin being the key and the insulin receptor being the lock. By placing the key, the insulin, into the lock, the insulin receptor on the cell surface, glucose can be transported into the cell and used to produce energy.
This is the first mechanism that sleep deprivation impacts as it decreases insulin sensitivity. In other words, the insulin receptors are not as receptive to insulin as they would normally be – the keys do not fit into all of the locks. What impact does this have? It means that we lack energy and feel more tired. This then leads us to eat more and often crave sugar as we search for a quick energy fix.
The second mechanism that sleep deprivation impacts is in relation to the hormone leptin. Leptin is stored in fat cells and via communication with the hypothalamus in the brain, suppresses appetite and hence food intake. The normal physiological function of leptin and its storage in the fat cells is to maintain metabolic health. The more fat cells, the more leptin and hence appetite and food intake should be suppressed avoiding weight gain and obesity.
However, sleep deprivation results in a decrease in leptin and hence appetite is not suppressed. We want to eat more.
Ghrelin is another hormone, often referred to as the hunger hormone, that impacts appetite. Ghrelin is released by the stomach and via communication with the hypothalamus stimulates appetite. Ghrelin is normally at its highest levels before a meal. However, sleep deprivation increases ghrelin production and therefore appetite. Again we want to eat more.
The impact of sleep deprivation on the 3 hormones, insulin, leptin and ghrelin results in an increase in appetite, increased food intake, a lack of energy and a craving for sugar.
It is a vicious circle. If we have an odd night with not enough sleep we shouldn’t suffer too badly.
However, if we are consistently sleep deprived this can become detrimental to our metabolic health resulting in weight gain, poor blood sugar management and the development of visceral fat. Visceral fat is the fat in the abdominal cavity that in excess results in inflammation and is linked to a higher risk of diabetes and heart disease. Melatonin, the hormone secreted at night that regulates the sleep-wake cycle also aids in the reduction of visceral fat. When we spend our evenings with artificial light we suppress the release of melatonin.
So the message is to prioritise sleep, make sure you’re getting enough as it might be having a bigger impact on your health than you have realised!
There are many tools useful in monitoring your sleep. The Oura Ring provides a guide allowing you to make lifestyle changes to improve sleep quality.