Sleep loss impairs glucose regulation (but exercise helps)

Doctor Rhonda Patrick here. Today we're going to talk about sleep and insulin sensitivity. When most people think about insulin sensitivity and what regulates it, they think about macronutrient composition or calories or exercise or fasting. People don't usually think about sleep, when in fact, sleep is a major determinant of insulin sensitivity. In fact, several studies have shown that sleep restriction over the course of several days can lead to acute insulin resistance in healthy individuals. Yet another study showed that sleep restriction for four hours a night, two nights in a row, reduced the insulin response by 30% and glucose tolerance by 40% in healthy individuals.

And yet another study showed that just a single night of sleep restriction causes acute insulin resistance in healthy individuals. This really highlights the important role that sleep plays in glucose regulation. There have been several mechanisms that have been worked out, ranging from how the liver and the muscle absorb glucose to how the beta cells in the pancreas respond to glucose and in turn produce insulin. In a recent discussion I had with Dr. Matthew Walker, he discusses how sleep restriction causes the beta cells in the pancreas to stop becoming sensitive to glucose, and this in turn affects how much insulin is produced. You know, I think the blood glucose story and sleep is very, very well worked out.

Now, it started with epidemiological studies where we started to see that people who were sleeping less than seven hours were at significantly higher likelihood of either being diabetic or going on to develop diabetes. Many of them were already in what we call a pre diabetic state, or they had what we now call sort of metabolic disorder. And then the question became, well, is that associational or is it causal? So the next studies that happened, and this was work done back in the 1990s by Eve Van Cauter at the University of Chicago. Wonderful studies took a group of healthy people, started to limit them to different doses of sleep for a week, you know, five hours of sleep, six hours of sleep, four hours of sleep.

And what she showed was that essentially after one week of short sleep, your blood sugar levels are disrupted so significantly that your doctor would classify you at that point as being pre diabetic after one week of short sleep. And the way that they do this is what's called a glucose tolerance test, where you are fasted and then you are given this sickly sweet drink of glucose, and then they are measuring from your blood in the next three or four hours, how quickly is your body able to dispose of that blood glucose. So what happens when you drink or when you eat a meal is that your blood sugar spikes and you don't want that spike to stick around very long. If your body is healthy, it deals with that raised level of blood glucose very quickly and it brings it back down very quickly.

That's a healthy profile. That's what we call good glucose management. So how good is your body at disposing essentially of that glucose? And the way it disposes it is that cells in the body, including muscle cells, will suck up that glucose. And it's called your disposal index or your disposition index, it turns out. So what she found, Eve Van Cauter, with her studies, was that, firstly, the way that your body knows how to absorb glucose and suck in that glucose is that there is another chemical called insulin, which is released by the pancreas and beta cells of the pancreas. And that insulin will instruct the cells of the body to open up special glucose channels to absorb the glucose and your blood sugar drops, which is good and healthy.

Firstly, what she found was that when you are not getting sufficient sleep, the beta cells in your pancreas stop being sensitive to the signal of high glucose. So the beta cells which normally are listening for this spike in glucose, and as soon as they sort of, you know, here now, they're not hearing it, they're sensing it. But as soon as they sense the spike in glucose, they release insulin and that insulin will drop your blood glucose. But those cells had become insensitive to glucose, what we call sort of glucose insensitivity. And so the beta cells of the pancreas stopped releasing as much insulin. It didn't release enough insulin to drop blood glucose, so blood glucose remained high. If that wasn't bad enough, we've since gone on to demonstrate.

And you can do this with really clever studies, taking tissue biopsies, the cells of the body, including muscle cells and fat cells, the receptors stopped being as sensitive to insulin. So firstly, you're releasing less insulin when you're sleep deprived, right? But what little insulin you do release is not instructing those cells to open up the channels to take away the monsoon of the glucose that's flowing in the channels of the body. So on both sides of the glucose regulation, on the release of insulin to instruct cells to absorb glucose, and on those cells themselves to be sort of instructed by insulin. Those cells became less sensitive to the insulin signal.

And so as a consequence, your overall ability to deal with glucose became far more degraded and blood glucose remained higher, which sets you on a profile of looking pre diabetic. Optimizing for good sleep is obviously very important, but there are other factors that also play a role. For example, exercise, particularly high intensity interval training. Studies have shown that high intensity interval training can actually ameliorate some of the negative effects that poor sleep has on regulating blood glucose levels. So the moral of the story is, get good sleep when you can, but if you can't, get a little exercise in there as well. I'm Dr. Rhonda Patrick, and I'll catch you next time.