We all know what hunger feels like. Our stomachs start growling and rumbling, our brains can feel a little foggy and all we can focus on is getting something to eat. But what tells our brains we’re hungry or full? It turns out that the gut and the brain are connected, forming the gut-brain axis and hormones help communication between the major organs. The satiety hormone, leptin and the hunger hormone, grehlin are the major players along this axis. One of the best ways to keep the gut-brain axis communicating properly? Sleep. The amount of grehlin and leptin produced by the body differ greatly when you don’t get enough sleep.
Individuals who have short sleep duration, 6 or fewer hours a night, have dysregulated amounts of leptin and grehlin. Their bodies are producing much more grehlin, leading them to feel hungrier and not producing enough leptin, so they never get the satiated signal. Not only are they hungrier, but because the brain thinks they’re fuel deprived, the body craves simple carbohydrates and sugars to get a quick boost of energy. So on average, sleep-deprived people are eating an extra 385 empty calories a day!
But why does sleep have such a significant impact on these hormones? It all starts deep in the brain, with the pituitary gland. The pituitary gland is the “master” endocrine gland, it oversees and communicates all hormone production and is markedly impacted by sleep. The pituitary gland receives feedback from two major pathways, the first being its connecting to the hypothalamus and the second being the autonomic nervous system (ANS). The ANS has two sub-divisions, the sympathetic, “fight or flight,” and parasympathetic, “rest and digest.” When you’re sleeping, the sympathetic system is less activated and the parasympathetic system is more activated, but when you’re not sleeping enough, this balance is thrown off. Sleep loss leads to increase in sympathetic nervous system activity, which greatly affects the endocrine system.
These changes in the endocrine system during sleep, lead to changes in appetite and metabolism when you’re awake. The satiety hormone, leptin, which is released by fat cells, is incredibly sleep-dependent. When there is less leptin, the body will produce more grehlin, signaling hunger. So when an individual is sleep-deprived, they have a greater caloric need, due to the extended amount of time spent awake, so the body upregulated hunger cues and downregulates fullness cues in order to meet these needs. Leptin rises as you sleep, signaling to the brain that you have enough energy for the time being. But when sleep is cut short, your brain doesn’t get the proper signals that it has enough energy.
Lack of sleep also leads to an increase in cortisol (the stress hormone) and an increase in insulin resistance.
Sleep helps regulate the delicate balance of hormones required to keep our bodies running effectively. Adults should be aiming for 7-8 hours of sleep each night.
-McGarty and Associates