1. Poor Weight Maintenance
Skimping on sleep can lead to weight gain, especially around the waist where stress-induced pounds often collect.
Studies show that sleep-deprived people tend to select sweet, fatty comfort foods. This quick-energy fare may compensate for the sluggishness and fatigue a poor night’s sleep produces, but it also increases daily caloric intake by as much as 20 percent.
“When you don’t get enough sleep, you don’t get the restoration sleep provides,” says Orfeu Buxton, PhD, professor of biobehavioral health at Pennsylvania State University. “The brain and body have to be active and alert for more time, and your body may need a little more energy, so your system overcompensates. You eat a few more calories.”
Even one night of sleep deprivation can trigger weight gain, according to a small but significant 2019 study Buxton and his team published in the Journal of Lipid Metabolism. Fifteen healthy men in their 20s spent 10 days eating the same calorie-dense meal. Most nights they slept 10 hours. But for four consecutive nights, they slept five hours or less.
Following the sleep-restricted nights, participants reported feeling hungry after eating the same meal that filled them up on the sleep-sufficient nights. What’s more, blood tests showed that their fatigued bodies were more apt to store the calories they ate as fat.
Eating at night, when the body expects to be sleeping, can also cause weight gain. In one study, mice whose meal patterns were flipped from day to night — they ate during their nighttime hours and fasted during the day — experienced a 48 percent increase in body weight. Mice eating the same calorie-dense meals during the daytime gained only 20 percent more weight over a period of six weeks.
Hormonal mechanisms appear to be at work in all of these cases. Production of the hunger hormone ghrelin increases when we’re tired. And, in a perfect storm of metabolic unfairness, sleep deprivation inhibits the production of leptin, the satiety hormone that signals fullness. With little or no leptin, we fail to get the cue that we’ve had enough food.
The final factor in sleep-deprived weight gain is behavioral: When we’re fatigued, the quality of our decisions can suffer.
“Sleep deprivation tends to make us do things that are riskier and more reckless,” says Chris Winter, MD, author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It. “In your normal rested state, you would be like, ‘I’m not going to eat this ice cream.’” But when you’re sleep deprived, he adds, you’re more likely to eat the whole pint.
2. Insulin Resistance
Just one night of shortened sleep — four hours of shuteye — can set the stage for insulin resistance.
“Not sleeping enough causes a rise in cortisol and changes insulin sensitivity,” says functional-medicine practitioner Myrto Ashe, MD, MPH. Prolonged periods of inadequate sleep can cause chronic insulin resistance, which can lead to prediabetes or type 2 diabetes.
Large-scale studies have repeatedly shown that type 2 diabetes is twice as common in adults who regularly report insufficient sleep; the connection between short sleep duration and type 2 diabetes is separate from other risk factors, such as high blood pressure, overweight or obesity, and family history. Once type 2 diabetes develops, studies show, the condition reduces sleep quantity and quality.
3. Microbiome Disruption
Poor-quality sleep appears to mess with the gut microbiome, too. Animal studies have linked inadequate sleep to changes in gut flora that trigger inflammation and affect insulin sensitivity.
They’ve also shown that obstructive sleep apnea — a nighttime breathing disorder associated with snoring and poor sleep — decreases levels of the bacteria that produce butyrate. A short-chain fatty acid, butyrate has been studied for its health-promoting properties: It improves non-rapid-eye-movement sleep, which includes the phases when the body passes into deep sleep and performs its tissue-repair work.
Low butyrate levels can lead to a self-reinforcing cycle of sleeplessness — and compromised gut health.