Rates of good metabolic health in American adults are concerningly low. Currently, only 12% of Americans meet the criteria for metabolic health. Even people within normal weight ranges aren’t necessarily metabolically healthy and may still show elevated glucose levels and cholesterol levels.
Not coincidentally, average sleep duration has decreased from 9 hours per night from 100 years ago to about 6.8 hours per night today.
Getting consistent, quality, and uninterrupted sleep is a critical component of preventing chronic diseases such as type 2 diabetes, obesity, heart disease, Alzheimer’s disease, and stroke–all of which are linked to metabolic dysfunction. Unfortunately, these already prevalent conditions are on the rise, currently affecting hundreds of millions of Americans.
What is Metabolic Health?
Your metabolism is a fundamental component of overall health. It’s essentially your body’s ability to process, utilize, and store energy from the food you eat.
We can get a sense of our metabolic health by looking at our blood sugar levels, insulin, cholesterol, blood pressure, and weight.
Since our metabolism is core to our overall health, metabolic dysfunction can wreak havoc on multiple fronts. If our metabolic metrics are out of whack, we can suffer from a myriad of unpleasantries such as weight gain, anxiety, balding, dementia and memory impairment, depression, and more. Further, chronically elevated glucose levels are linked to diabetes, a condition characterized by metabolic dysfunction.
To further complicate one’s personal understanding of their own metabolism, everybody is unique and responds to factors differently. For example, the same banana could make Person A’s glucose levels spike and have minimal effect on Person B. This is why any standardized “perfect” diet is theoretically impossible.
Insulin is a vital part of the equation: it’s the hormone released when glucose enters the body, and it tells cells to absorb glucose.
When our glucose levels and insulin levels are chronically high, we can develop “insulin resistance,” which means our cells become “numb” to insulin signaling. Ultimately, we would need more insulin to get sugar in the cells. The more insulin resistance we develop, the harder it is for our body to funnel and convert glucose into energy, and we end up with a lot of excess glucose in our bloodstream and converted to fat.
However, the bright side is that since our metabolism is so foundational, pursuing metabolic fitness can theoretically help put us in an advantageous position in an extremely multifaceted biological playing field. Modern technology like continuous glucose monitoring (CGM) allows us to take a peek under the hood to see how our body reacts to food decisions in real-time.
Metabolic health is also impacted by multiple variables outside of nutrition, such as exercise, stress, and sleep.
Your sleep, in particular, can have profound effects on your body’s metabolic health.
How Much Sleep Should I Get to Be Metabolically Healthy?
Even intermittent sleep deprivation can have detrimental effects on our metabolic health.
For example, one study followed eleven healthy young men subjected to six nights of sleep deprivation with four hours of sleep, followed by a week of twelve hours of sleep per night. On the fifth day of each scenario, the participants did an oral glucose test (a diagnostic test often used to diagnose diabetes) to get a glimpse at how their metabolism reacted to a fixed amount of oral sugar.
The results? The participants exhibited signs of an impaired metabolism and insulin resistance during the sleep deprivation period. The rate of clearing sugar out of the bloodstream was 40% slower than when they were well-rested.
This relatively short six-night sleep deprivation period generated metabolic profiles in the otherwise healthy young men that resembled people with type 2 diabetes.
Another study followed healthy, normal-weight individuals who fell into categories of short sleepers (those who slept less than 6.5 hours per night) and normal sleepers (7.5 to 8.5 hours of sleep per night).
The short sleepers had to secrete 50% more insulin than normal sleepers to achieve similar glucose results, placing them at risk for developing insulin resistance in the long-term.
Insulin resistance, which acts as a brake on our body’s ability to burn fat for energy, also contributes to weight gain.
In pursuit of metabolic fitness, we want our insulin levels to be fairly low and stable. Sleep deprivation appears to make this very difficult.
Even just a few days in a row of inadequate sleep can negatively impact our metabolic health. However, excessive sleep isn’t necessarily always better for metabolic health.
The magic number for metabolically-optimized sleep appears to be between seven to eight hours per night. Any less than seven, the risk of diabetes increases sharply for every hour lost. Above eight hours, the risk also increases.
How Sleep Quality Impacts Your Metabolic Health
Sleep duration is only part of optimal sleep hygiene.
Sleep quality also seems to have a significant impact on metabolic health. One study followed adult men for eight years and found that subjects who reported interrupted sleep and difficulty maintaining sleep had double to triple the risk of developing type 2 diabetes.
The regulation of glucose and insulin are partially controlled by cortisol (often pegged as our “stress hormone”), which tells our body that something “stressful” is happening and preparing to have the energy to utilize against this real or perceived threat.
To help the body prepare, cortisol mobilizes the stored glucose from the liver into the bloodstream. It also decreases insulin production in the pancreas and reduces insulin sensitivity in the body, which means that the glucose is less likely to be utilized by cells and more likely to remain in circulation, elevating blood glucose levels.
Since our cortisol levels tend to be lower during the evening and early part of the night, our glucose levels tend to stabilize around a lower range at night. Sleep deprivation for just six days can increase cortisol levels, which in turn can elevate blood sugar.
Sleep deprivation can also trigger an increase in growth hormone, which decreases glucose uptake by the muscles, further contributing to a rise in blood glucose levels.
A lack of high-quality sleep may also increase your appetite, leading to a higher likelihood of overeating.
One study of twelve healthy young men with two days of restricted sleep reported an increase in hunger and appetite for calorie-dense high-carbohydrate foods, an elevation of a hunger hormone ghrelin, and a decrease in the satiety hormone leptin.
Sleep deprivation and inflammation in the body are also tightly linked. Some experiments highlight an increase in pro-inflammatory chemicals like TNF-a, IL-6, and CRP, all of which happen to be immune markers that are also increased in type 2 diabetes and obesity.
There seem to be many shared underlying mechanisms between sleep loss and metabolic dysfunction, so it begs the question: how do we improve our sleep?
Optimizing our metabolic health by getting better sleep can start with making small changes: making sure your bedroom is dark and quiet, ensuring any possible distractions are far away, and limiting your caffeine intake near bed-time.
Erratic sleep patterns often turn our focus to our daily schedules. Carving out an adequate amount of time for seven to eight hours of high-quality sleep can be tricky for the busy, but the research suggests that it’s very worth our effort.
However, to truly understand how our sleep efforts positively impact our metabolic health, we can leverage objective and personal continuous glucose data to discern the relationship real-time.
Beyond potentially preventing chronic diseases, stable and healthy glucose and insulin levels can positively impact many aspects of our wellness, such as inflammation, memory, immune function, energy levels, skin health, sexual health, and more.