Within just four days of sleep deprivation, your body’s ability to properly use insulin (the master storage hormone) becomes completely disrupted. In fact, the University of Chicago researchers found that insulin sensitivity dropped by more than 30 percent.
Here's why that's bad: When your insulin is functioning well, fat cells remove fatty acids and lipids from your blood stream and prevent storage. When you become more insulin resistant, fats (lipids) circulate in your blood and pump out more insulin. Eventually this excess insulin ends up storing fat in all the wrong places, such as tissues like your liver. And this is exactly how you become fat and suffer from diseases like diabetes.
Lack of Rest Makes You Crave Food
Many people believe that hunger is related to willpower and learning to control the call of your stomach, but that's incorrect. Hunger is controlled by two hormones: leptin and ghrelin.
Leptin is a hormone that is produced in your fat cells. The less leptin you produce, the more your stomach feels empty. The more ghrelin you produce, the more you stimulate hunger while also reducing the amount of calories you burn (your metabolism) and increasing the amount fat you store. In other words, you need to control leptin and ghrelin to successfully lose weight, but sleep deprivation makes that nearly impossible. Research published in the Journal of Clinical Endocrinoloy and Metabolism found that sleeping less than six hours triggers the area of your brain that increases your need for food while also depressing leptin and stimulating ghrelin.
If that’s not enough, the scientists discovered exactly how sleep loss creates an internal battle that makes it nearly impossible to lose weight. When you don’t sleep enough, your cortisol levels rise. This is the stress hormone that is frequently associated with fat gain. Cortisol also activates reward centers in your brain that make you want food. At the same time, the loss of sleep causes your body to produce more ghrelin. A combination of high ghrelin and cortisol shut down the areas of your brain that leave you feeling satisfied after a meal, meaning you feel hungry all the time—even if you just ate a big meal.
And it gets worse.
Lack of sleep also pushes you in the direction of the foods you know you shouldn’t eat. A study published in Nature Communications found that just one night of sleep deprivation was enough to impair activity in your frontal lobe, which controls complex decision-making.
Ever had a conversation like this?
“I really shouldn’t have that extra piece of cake… then again, one slice won’t really hurt, right?”