Sleep’s Important Role in Weight and Metabolic Health
An essential part of health is getting not only enough sleep but also enough GOOD quality sleep. In fact, adequate sleep is one of the 6 pillars of Lifestyle Medicine.
In theory, most of us know that we should be getting enough sleep. I say most of us, because, unfortunately, there are some people out there who pride themselves on the fact that they don’t need a lot of sleep. As if only sleeping 5 hours a night is a badge of honor to boast about. The harsh reality is that the negative effects of sleep deprivation (which anything less than 7 hours is) will manifest at a certain point in time as either: emotional lability, difficulty concentrating, high blood pressure, high blood sugars, and even difficulty losing weight. No virtue in any of those things.
Sleep has been studied in great detail and I want to share with you some of the important hormones that are regulated during sleep and impacts sleep deprivation has on how these hormones affect our health.
Cortisol
Cortisol is a hormone that is secreted by the adrenal glands and is known as one of the stress hormones. Among the many functions it serves, one of the functions it has is to signal to the liver to release its glucose stores. The purpose of this is to make sure that there is enough energy (in the form of glucose) circulating in the blood so that the cells in the body can use it immediately in urgent or emergent situations of stress, especially if a person needs to flee a bad situation. Since glucose is the preferred energy source of cells, this is a helpful adaptation that supplies cells with the energy they need, even if we have not had a chance to eat recently.
In a normal circadian sleep-wake cycle (meaning waking up around 6-8:00 am and going to sleep around 9-10:00 pm) cortisol levels start to rise around 4:00 am and by 8:00 am, it is usually at its highest concentration of the day. As the day progresses, the cortisol levels naturally decline and reach their lowest concentrations late at night close to undetectable), typically between 11:00 pm to 4:00 am.
However, if sleep is affected by travel, jet lag, shift work, or inability to get a sufficient amount of sleep, cortisol levels will never reach their low concentration at night. The chronically elevated cortisol concentrations then continuously signal to the liver that it needs to release its stored glucose which in turn has a detrimental effect of leading to higher fasting blood sugars. Higher cortisol levels overnight also leads to reduced systemic vascular resistance, which leads to higher blood pressure.
Ghrelin
Ghrelin is a hormone secreted by the stomach and is known as the hunger hormone. This hormone drives food seeking behavior by stimulating appetite. Studies have shown that when individuals do not get adequate sleep, ghrelin levels are higher the following day. What does that translate to? Feeling hungrier and because feeling hungry is not a pleasant sensation, to get rid of the hunger pangs, people will eat - more.
Leptin
Leptin is a hormone that is secreted by the adipose tissue (aka fat tissue). Adipose tissue is a highly active endocrine organ and leptin’s role in the body is to trigger satiety, or the sensation of feeling full. So, as opposed to the hunger hormone above, once we start eating because we are hungry, leptin will be one of the hormones that will tell us to stop eating, because we feel full. Unfortunately, after a night of insufficient sleep, Leptin levels are not as high. This means that once we start eating, we do not get signals of feeling full as soon or as strong as we otherwise would have, which can lead to consuming more calories than usual.
This complicated combination of feeling hungrier and not getting as full when we eat (combined with the fact that when we are sleep deprived, we also tend to not make the healthiest food decisions) occurring frequently over time will lead to over consumption of calories and this caloric excess contributes to weight gain.
Please also consider that working on improving sleep (and working on it is required, since it is not something that we can just will and make happen overnight, unfortunately) is an intervention that is low in cost, results in significant benefits to health, and comes without concerns of interactions with other medications. It is a low-cost, low risk intervention, and we need to really start prioritizing sleep a lot more for health benefits than the majority of us do.
The goal is to get 7-9 hours of sleep per night, with the goal really being close to 8 hours on a consistent basis. You will see that there is a recommended cap to the amount of sleep we should aim for, since sleeping too long has its own adverse health implications.
So here are some of my tips to try to improve the quality and length of your sleep:
Set a consistent bedtime. This will help establish a reliable circadian rhythm which benefits consistency also of hormone secretion.
Hydrate sufficiently throughout the day. My patients will tell you that I am very insistent on making sure they are hydrating well with water. Hydration is important to ensure enough circulating blood volume, an important determinant of core body temperature at night. If we are relatively dehydrated, our core body temperature remains elevated while we sleep, decreasing sleep quality.
Shut off blue light technologies at least 1 hour prior to bedtime. Blue light is a potent inhibitor of our sleep onset hormone: melatonin. Melatonin is what helps inform the body that it is time to fall asleep when concentrations are high. Screens on our technology (phones, TVs, laptops, tablets, etc) all emit blue light and will significantly suppress melatonin, delaying the onset of sleep and thereby likely reducing the amount of sleep a person gets at night.
Drink non-caffeinated tea in the evening. Avoiding caffeine in the afternoon and evening is important since its stimulant activity will mask the sleep pressure that is building and trick a person into thinking they are not tired. However, drinking a warm, non-caffeinated tea in the evening can have a beneficial effect in dilating blood vessels in the arms and legs, which helps lower core body temperature. A cool core body temperature is associated with better sleep.
As we look for effective and safe interventions to improve health, please consider how incredibly important it is to make getting adequate amounts of good quality sleep a priority!