This is a guest post by Casey Means, MD, Co-Founder and Chief Medical Officer of Levels
Everyone knows that eating a nutritious diet and exercising regularly is important for health and disease prevention, but most people don’t know that a good night of sleep is especially important in maintaining your metabolic health.
This is particularly important now: when you look at all Americans, only 12% meet the criteria for being metabolically healthy! What does it mean to be metabolically healthy? It means your body is equipped to utilize and store energy properly and can be gleaned by looking at things like weight, blood pressure, cholesterol, insulin, and blood sugar levels.
We want our metabolic metrics on point because our daily lives can greatly suffer when these are off base. Insulin and blood sugar levels not optimal? These two factors alone could mean you’re set up for weight gain, infertility, balding and hair loss, dementia and memory impairment, erectile dysfunction, acne, depression, anxiety, chronic pain, and increased appetite.
What sleep deprivation does to your health
When you’re dealing with something as fundamental as metabolism, dysfunction can lead to a wide variety of symptoms in the short and long term. This is why it’s so important to understand the integral role of sleep in maintaining metabolic health.
What’s more, getting consistent, quality, uninterrupted sleep is a key factor in preventing chronic diseases like obesity, type 2 diabetes, heart disease, stroke, and Alzheimer’s, all diseases that are also related to metabolic dysfunction. These conditions are sharply on the rise, together affecting hundreds of millions of Americans, and perhaps not coincidentally, sleep duration has inversely decreased from an average of 9 hours per night a century ago to just 6.8 hours per night today.
Increasing rates of obesity over time. Source: NIH
Increasing rates of diabetes over time. Source: CBC
But what if we just lose a bit of sleep every once in a while? The truth is, even intermittent sleep deprivation can cause metabolic health problems. In one study, 11 healthy young men were subjected to 6 nights of sleep deprivation with just 4 hours of sleep, followed by 7 nights of 12 hours of sleep. On the 5th day of each of these scenarios, they underwent a diagnostic test called an oral glucose tolerance test — a test commonly used to diagnose diabetes — to see how their metabolism handled a controlled amount of oral sugar.
During the sleep deprivation condition, the subjects did terribly on the glucose tolerance test: they exhibited signs of insulin resistance and impaired metabolism. The rate at which they were able to clear the sugar out of the bloodstream was 40% slower than when they were well-rested!
The role of insulin
Insulin is the hormone that is released when glucose enters the body, and it tells cells to absorb glucose; when glucose levels and insulin levels are chronically high, it can lead to “insulin resistance,” whereby the cells become “numb” to all this insulin signaling and end up needing more insulin to get the sugar in the cells. Alarmingly, this short, 6 night period of sleep deprivation generated metabolic profiles in healthy young men that were similar to people with type 2 diabetes. In short, we don’t want to miss out on adequate sleep, even if it’s just for a few days in a row.
In another study of healthy, normal-weight individuals, those who frequently slept short amounts (less than 6.5 hours per night) performed similarly on an oral glucose tolerance test to normal sleepers (7.5-8.5 hours of sleep per night), but the short sleepers had to secrete 50% more insulin than the normal sleepers to achieve these similar glucose results. This is not good, because high levels of insulin over time can lead to insulin resistance, and also act as a brake on the body’s ability to burn fat for energy, thereby contributing to weight gain. We want insulin levels to be fairly low and stable, and sleep deprivation appears to sharply counteract this.
So if less sleep is bad, is more sleep always better for metabolic health? Not necessarily. It appears the magic number for metabolically-optimized sleep is between 7 to 8 hours per night. Below this, and risk of diabetes increases sharply for each hour lost. Above 8 hours of sleep per night, the risk also increases. We want to hit that sweet spot.
The risk of type 2 diabetes increases with too much or too little sleep. Source: ADA
The impact of sleep quality
Aside from sleep duration, sleep quality seems to have a big impact on metabolic health. A study of adult men followed for 8 years showed that those subjects who reported interrupted sleep and difficulty maintaining sleep had 2-3 times the risk of developing type 2 diabetes.
Why does sleep deprivation lead to problems with glucose, insulin, and metabolic health? It may be because the regulation of glucose and insulin are in part controlled by cortisol (our “stress hormone”