How Losing Sleep Can Pack On Pounds

07/24/2011 10:43 am ET | Updated Sep 23, 2011

Want to know my number one diet tip? It has nothing -- and everything -- to do with the foods you eat and exercise you do.

The best thing you can do to have a lean, fit body is to get a good night's sleep. I'm talking quantity and quality here. If you sleep eight hours, but wake up three times during the night to go to the bathroom, you're not getting high-quality sleep -- and the repercussions can show up around your waistline.

If you think the worst aftermath of a crappy night's sleep is that you snap at your partner the following morning and make a few lapses in judgment during the day, think again. Here's the truth: lack of sleep can make you fat because how you sleep directly impacts how much you eat and what kind of foods you eat.

In other words, whether you get a solid eight hours or a toss-and-turn six hours can determine whether you go face-down in the Haagan-Dazs or choose frozen blueberries and Greek yogurt. Even if you do reach for the yogurt, sleep can determine whether you eat sensibly or devour the whole container. (Remember that healthy food becomes unhealthy when you overindulge.)

Solid or substandard slumber also signals your body to either store fat or burn it for fuel because of its impact on insulin, leptin and cortisol (more on this later). Getting a quality eight and a half hours of sleep supports better fat-burning the following day. Sleep even contribute to your degree of hunger. If you find yourself wandering to the Danish cart at 3 p.m. after you ate a substantial lunch, you might want to look at how well you slept the night before.

Hormones play a huge part in this process. Ghrelin, a hormone that tells your brain to eat now, increases when you sleep poorly. Leptin, on the other hand, helps put the brakes on the brownie cheesecake. No surprise: when you don't sleep, you become more leptin-resistant.

Poor sleep also impacts insulin. Chronically-elevated insulin makes it more difficult to burn fat. Long-term sleep deprivation can make your cells insulin-resistant which leads to higher fasting insulin levels. Besides impairing fat-burning, these high levels can also lead to diabetes, heart disease and certain cancers.

Have I convinced you yet that sleep plays a huge role in whether or not you are at your ideal weight? A study at the University of Chicago, with the unwieldy title "Exposure to recurrent sleep restriction in the setting of high caloric intake and physical inactivity results in increased insulin resistance and reduced glucose tolerance," concluded that even if you eat healthy and exercise, not getting the recommend seven to nine hours of sleep per night puts you at risk for obesity. In other words, poor sleep patterns can screw up even your best efforts to have the body you want.

It seems that many people think, "If I cut back one hour of sleep, I can get that report finished, or a couple hours less sleep on the weekend to have drinks with the girls won't hurt me once in a while." It's tempting, but the reality isn't pretty. Even one hour fewer of sleep can trigger hormonal chaos. You eat more, move less, make terrible eating choices and exacerbate stress levels.

As a nation, we are more stressed out than ever and poor sleep is one of the more controllable sources of stress (you can't really fire your boss, can you?). When you are under stress, your body can secrete more cortisol and adrenaline. Higher cortisol levels make you better at storing fat and raise the set point for burning it off. What's more, high cortisol levels impair digestion.

Your cortisol levels remain high for longer periods when you get less-than-optimal sleep. What ensues is a vicious cycle. High cortisol burns up your energy-assisting B vitamins, and you can't make the neurotransmitters you need to sleep well. This "Jeckyll and Hyde" hormone also lowers levels of serotonin, the feel-good hormone your brain eventually converts to melatonin for -- you guessed it -- good sleep.

Let's look at how this downward spiral plays out. You sleep terribly so you hit the snooze button multiple times. You're too tired to make your morning shake, so you grab a "low-fat" muffin (nothing more than a sugar-laden cupcake in disguise) and a large latte for that caffeine pick-me-up. By mid-morning, you're drowning in stress, dealing with a sugar crash, angry at everyone in sight and finally say "to hell with it" and grab a doughnut a co-worker brought in.

And don't think you can just crank back the calories and do some cardio to make up for that sleep-deprived hormonal flux. It drives me crazy when I hear about people who cut back on sleep to get in a good workout before work. If you want strong, sexy arms, you have to pack in those ZZZs. Sleep helps your body repair, rebuild and recover from the strenuous effort you put in at the gym. Like vigorous exercise, sleep also increases growth hormone, or HGH. So let's say you got a pitiful five hours of sleep and scheduled your trainer for 6 a.m. You certainly won't be able to train with the intensity you would with substantial rest, particularly when you're yawning and wondering why that fourth cup of coffee never kicked in.

You also won't recover as well from a tough workout when you don't sleep well. You don't give your body the chance to repair muscle mass and you accelerate the aging process. It's a lose-lose situation if I've ever seen one.

So you get it: you need sleep. But it's sometimes hard to put the brakes on life and unwind after a frenetic day. Look for a ritual that helps you relax, whether that includes soothing music, a meditation CD or a hot bath. Just don't make too much alcohol part of that sleep ritual. A glass of pinot noir at dinner will help you relax, but add in a nightcap or two and you will wake up dehydrated at 3 a.m. Exactly what you don't need for a good night's sleep.

The take-away: Make time for sleep as your number one strategy for both a lean, healthy body and optimal health.

• Department of Medicine, University of Chicago, Chicago, IL 60637; General Clinical Research Center, University of Chicago, Chicago, IL 60637.
• Results: Conclusions: Experimental bedtime restriction, designed to approximate the short sleep times experienced by many individuals in Westernized societies, may facilitate the development of insulin resistance and reduced glucose tolerance.