Most of us have heard that getting enough sleep can help you maintain a healthy weight. But…why?
Logging the recommended seven to nine hours of shuteye per night can help you reap a lot of benefits: Getting enough sleep can boost your alertness, attention span, and creativity. It can bolster your immune system, making you better equipped to fight off illness. And it can even help reduce your odds for serious diseases, like diabetes and heart disease.
But a growing body of evidence also suggests that there’s a link between how much you sleep and your weight. Adults and kids who catch too few Zzzz’s tend to be heavier than those who get enough.
How much heavier? Check out the numbers for yourself: In a 2006 study that followed the sleep habits of more than 60,000 women for 16 years, those who slept for less than five hours per night were 30% more likely to gain 30 pounds compared to those who slept for seven hours per night. That’s roughly the equivalent of three jean sizes.
OK, so lack of sleep definitely makes you gain weight. But how? Turns out, there’s several factors at play. Take a look!
Feeling tired = less energy to exercise.
This theory is definitely the most straightforward: If you’re exhausted from not sleeping, the last thing you feel like doing is hitting the gym. And so, people who don’t get enough sleep end up exercising less, and in turn burn fewer calories.
Recent research backs this up. According to a study published earlier this year in the journal SLEEP, people who stay up late move less and feel like it’s harder to maintain an exercise routine compared to those who turn in early. When researchers tracked 123 adults, they found those who described themselves as night owls spent the most time sitting. The night owls also had more perceived barriers to working out, like not having enough time or being unable to stick to an exercise schedule.
Making matters worse, the whole thing can become a vicious cycle. Lack of exercise can negatively affect the quality of your sleep (while exercising regularly can help you sleep better). Which means you end up even more tired and with less energy to work out. Before you know it, you’ve packed on a few pounds.
Feeling tired = less energy to make smart food choices.
When you come home pooped after an especially long, crazy day, what do you want to eat? Probably something warm, comforting, and above all, easy. Like…delivery pizza or boxed mac and cheese, not kale and quinoa salad that takes half an hour to make.
That’s because when you’re zonked, it’s hard to think straight. So when your stomach starts to rumble, you may be more likely to reach for the yummiest, easiest thing instead of the healthiest (or even sort of healthy) thing.
But that’s not all. In addition to making it tougher to make complex decisions, sleep deprivation also amplifies the part of your brain that responds to rewards, found one recent University of California-Berkeley study. Which means that greasy, gooey, or otherwise not-very-good for you fare is even more tempting than usual, making it harder for you to say no.
Being awake later means more time to eat.
But too little shuteye doesn’t just make it harder to make healthy meal and snack choices. Most likely, it also means that you’re staying up longer—and simply have more time to nosh.
Of course, just because you’re awake in the wee hours doesn’t mean you have to keep eating. But according to the research, you probably will. Compared to those who turned out the lights at 10 P.M., adults who stay up until 4 A.M. eat about 550 more calories, found a 2013 SLEEP study. And over the course of just five nights, that added up to more than two pounds gained.
Adding insult to injury? When you stay up late, you’re almost certainly not going to be snacking on carrot sticks (which, incidentally, could actually help you sleep better). According to recent research out of Oregon Health & Science University, the body’s internal clock appears to naturally be set to desire sweet, starchy, or salty foods after about 8 P.M. Hello, midnight potato chips!
Lack of sleep messes with hormones and metabolism.
Ever heard of the pituitary gland? It lives in your brain. And though it’s only about the size of a pea, it holds control over the production and release of most of the hormones in your body—including cortisol, the stress hormone that’s linked to weight gain.
In the evening, your pituitary gland causes cortisol levels to slowly decrease, helping your body wind down for the night. But in people who are sleep deprived, those nighttime levels drop much slower. The result? Cortisol never drops as low for them as it does for people who get enough sleep. Over time, that can cause high blood sugar, which could lead to obesity.
That’s not all. Recent studies also suggest that appetite-regulating hormones are heavily influenced by sleep. After a few days of sleep deprivation, leptin—the hormone that tells your brain when you’re full—falls to super low levels, making it harder to know when to stop eating.
At the same time, your body pumps out more ghrelin, the hormone that stimulates appetite. Which means overtired you ends up craving more food, especially foods that are high in carbs.
So, what can I do?
The solution, it seems, is pretty simple. If you want to maintain or achieve a normal weight, it’s a good idea to strive for seven to nine hours of sleep per night.
Of course for some, achieving that is easier said than done. To which we say, there are so many ways to increase your odds for sleeping well: Start practicing good sleep hygiene, make sure you’ve got the best mattress, or download some sleep-promoting apps. Chances are if you make it a priority, sleep—and a healthy waistline—will come.
Have you ever lost or gained weight as a result of changing sleep patterns? Do you follow a strict sleep schedule along with your diet?