Nearly 71 percent of U.S. adults aged 20 and over are overweight or obese. Among children, nearly 21 percent of 12- to 19-year-olds are considered obese, along with 17 percent of 6- to 11-year-olds and 9 percent of 2- to 5-year-olds.¹ Exercise and, particularly, diet, definitely play a role in this epidemic, but there’s another often-overlooked factor that may help people to keep their weight in check with little added effort. In fact, it requires nothing but getting more sleep.

Like overweight and obesity, insufficient sleep is a public health problem in the U.S. — and it could be that the two are related. The U.S. Centers for Disease Control and Prevention (CDC) reported that 50 million to 70 million adults have sleep or wakefulness disorder, while more than 35 percent said they sleep fewer than seven hours during a typical 24-hour period.²

Meanwhile, this lack of sleep is having serious consequences, like unintentionally falling asleep during the day (reported by 38 percent of survey respondents) or nodding off while driving (reported by nearly 5 percent). Your weight, however, may also suffer.

Sleeping Well Associated With Smaller Waist, Lower Weight

U.K. researchers looked into the connection between how long you sleep (sleep duration), diet and metabolic health among more than 1,600 adults.³ Past research has linked not enough sleep with an increased risk of metabolic diseases, including obesity, and this study found similar results. Sleep duration was negatively associated with body mass index (BMI) and waist circumference, which means the longer a person slept, the smaller their waist and lower their BMI were likely to be.

Specifically, people who slept for an average of just six hours a night had a waist circumference more than 1 inch (3 centimeters) larger than those who slept for nine hours a night.⁴ Shorter sleep was also linked to lower levels of beneficial HDL cholesterol,⁵ and researchers noted, “[O]ur findings show that short-sleeping U.K. adults are more likely to have obesity, a disease with many comorbidities.”

Along these lines, a study published in the journal Sleep even found that sleeping in longer on weekends — also known as “catch up sleep” (CUS) — may positively impact your weight. On average, the group of participants who slept up to two hours longer on weekend days than weekdays had a significantly lower BMI than the non-CUS group.⁶ Lack of sleep influences hormone levels, including increasing the “hunger hormone” ghrelin and decreasing leptin, which is involved in satiety.

By activating your endocannabinoid system, which is involved in modulating appetite and food intake, sleep deprivation can even give you the munchies, similar to marijuana use. In the featured study, while the researchers hypothesized that shorter sleep may lead to increased unhealthy eating, they found no such link in this case.

How Does Sleep Affect Your Waistline?

Sleep is intricately involved in your body’s ability to function properly. Skimp on it, and your self-control will suffer, as will your willpower to make healthy eating choices. On a biological level, however, lack of sleep also disrupts important hormones — like, as mentioned, ghrelin and leptin — and metabolic function. Losing as little as 30 minutes of sleep each night can disrupt your metabolism enough to cause weight gain.

In fact, each half-hour of sleep debt incurred during weeknights raised one study’s participants’ risk for obesity and insulin resistance by 17 percent and 39 percent respectively after one year.⁷ What this means is that if you need eight hours of sleep but consistently only get seven, you may theoretically raise your risk of obesity by about 34 percent and simultaneously jack up your chances of insulin resistance — which is a hallmark of most chronic diseases, including type 2 diabetes — by 78 percent.

In another revealing study, people who slept only five hours a night gained nearly 2 pounds a week while consuming extra calories, primarily late at night. On the contrary, people who slept nine hours a night maintained their weight and tended to eat fewer high-carbohydrate foods and unhealthy fats.⁸ The results are true even among children, which research revealed that children with the least amount of sleep are 4.2 times more likely to be obese.⁹

If you’re trying to lose weight, getting adequate sleep may make or break your results, with research from the University of Chicago showing that dieters who slept for 8.5 hours lost 55 percent more body fat than dieters who slept 5.5 hours.¹⁰ “Lack of sufficient sleep may compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction,” the researchers wrote, continuing:¹¹

“The neuroendocrine changes associated with sleep curtailment in the presence of caloric restriction, however, raise the possibility that lack of sufficient sleep may compromise the efficacy of commonly used dietary interventions in such individuals. For instance, higher ghrelin concentrations may facilitate the retention of fat and increased hunger could compromise adherence to caloric restriction.”