Don’t believe it? We didn’t either, until we saw our testers lose up to 15 pounds just by getting more sleep every night. It’ll work for you, too—turn the page to get started!

by Jenny Stamos Kovacs (from Glamour magazine)

When a doctor recently swore to a Glamour editor that he could help women lose weight just by making over their sleep habits, we were dubious. Research has linked lack of sleep to weight gain, but certainly weight loss requires hard work, diet and exercise—right? We decided to put it to the test. Sleep and medical experts Michael Breus, Ph.D., and Steven Lamm, M.D., created a plan for seven Glamour readers of varying weights. The women’s one simple goal: Get at least seven and a half hours of sleep a night. That’s it. In fact, we asked the women not to make any significant diet or exercise changes—we wanted to see if sleep and sleep alone would make a difference. Did it ever! Week by week, we were amazed by the results the women reported. At the end of 10 weeks, Réal Hamilton-Romeo, 30, dropped seven pounds; Kate Foley, 25, lost six; Lisa Braverman, 34, took off nine pounds; Brelyn Johnson, 28, lost 10 pounds; Paige Barr, 35, shed 12; and—are you ready for this?—Ehmonie Hainey, 33, lost 15.

We don’t want to give the impression that this makeover was effortless; finding time for more sleep does take work. In fact, one of our testers, Natasha Crawford, 33, wasn’t able to stick to the plan for more than two or three nights a week because of a crazy job schedule. But even though she didn’t lose weight, by the end of the plan she had still lost a total of two and a half inches off her waist, bust and hips.

At least two dozen studies have documented that people tend to weigh more if they sleep less, says Sanjay Patel, M.D., a researcher at Case Western Reserve University in Cleveland. In a 16-year study of almost 70,000 women, Dr. Patel and his colleagues found that those who slept five hours or less a night were 30 percent more likely to gain 30-plus pounds than those who got more rest. In fact, some experts believe lack of sleep is one reason for America’s obesity epidemic. The average woman gets six hours and 40 minutes of sleep most nights, according to the National Sleep Foundation—much less than the seven-and-a-half-hour minimum our experts say healthy women need.

What exactly is the sleep-weight connection? Science shows that sleep deprivation wreaks havoc on hormones that control appetite, cravings and the metabolism of fat. See how these findings translate to your body.

Sleep More, Eat Less

Whether you notice it or not, you probably eat more, sometimes much more, when you’re tired. Proof: Researchers at the University of Chicago allowed people to sleep five and half hours one night and eight and a half on another, then measured how many free snacks the participants downed the next day. They ate an average of 221 calories more when sleepy—an amount that could translate into almost a pound of fat gained after two weeks! “When women are deprived of sleep, they have an increase in ghrelin—what we call the ‘go’ hormone—because it makes you want to go eat more,” says Breus, clinical director of the sleep division at Southwest Spine & Sport in Scottsdale, Arizona, and author of Beauty Sleep. “They also have a drop in leptin, the ‘stop’ hormone that tells you to stop when you’re full.” Not only do you want more food when you’re sleep-deprived, you also want junkier food: Your body craves simple carbohydrates (chocolate, pastries, candy) that it can break down fast for quick energy, explains Breus. “I used to eat a ton of sugar every afternoon,” Glamour volunteer Johnson says. “But now I can have just a small piece and feel satisfied.”

Sleep More, Store Less Fat

Even before seeing the number on the scale drop much, our testers noticed other changes. Three weeks into the plan, Braverman easily put on a pair of pants that used to be too snug. And at the two-month mark, Hamilton-Romeo told us, “My stomach is getting flatter and my love handles smaller.” By the end of 10 weeks, she’d shaved almost five inches off her waist, hips, bust and thighs—even though, at 5’4” and 133 pounds, she wasn’t overweight to begin with. The explanation? “During deep sleep, your brain secretes a large amount of growth hormone, which tells your body how to break down fat for fuel,” explains Breus. “Deprive your body of deep sleep, and when extra calories get stored as fat, there isn’t enough growth hormone to break it down. So your body takes a shortcut and packs it away in your butt, thighs, belly—wherever you tend to put on weight.” Says Braverman, who lost a total of two and a half inches: “The changes in my body fascinate me, because I really haven’t changed anything except my sleep habits. I eat the way I always have and exercise the same amount, maybe even less because my schedule is tighter now that I have to go to bed earlier!”

Sleep More, Have More Energy

Perhaps not surprisingly, all of the women on our plan said they felt much less tired. And though we told them not to make any conscious exercise changes, a couple of them couldn’t help themselves. “I’ve always worked out,” Barr told us, “but I’m spending more time at the gym because I finally have the energy!” Says Foley, “I used to have days when I’d want to go home and just veg out on the couch; now I’d rather run or do something physical—a complete revolution in my lifestyle.” Breus wasn’t surprised. “Your perception of how hard or easy exercise is to do is directly affected by how sleep-deprived you are,” he says. Ready to get some of these same benefits?

The Sleep Diet:

The minimum amount of sleep you need for weight loss is seven and a half hours a night, our experts say. But the closer you can get to your ideal sleep time—see #4, below, to figure that out—the better your results will be. (Sorry, but sleeping more than that won’t help you drop more pounds!) And you don’t have to be clinically overweight for this to work. What to do:

1. Go to sleep and wake up at the same time every day.

Write down the time you need to get up in the morning, then count back seven and a half hours. That is the time you need to be in bed. But we’re not out to kill all your fun: On Friday or Saturday nights, you can go to bed one or two hours later than usual and sleep in one or two hours the next morning—as long as you get your required seven and a half hours.

2. Start a bedtime routine.

Create a presleep ritual—such as light reading, a hot bath, stretching—beginning somewhere between 45 minutes to an hour before the time you’ve planned to close your eyes. Pretty soon, your body will start to associate specific actions with relaxation and falling asleep. And turn off your TV, computer, BlackBerry and cell phone before that time begins. “When your brain senses light shining in your eyes, it stimulates the wake response and lowers melatonin, the hormone that cues you to feel drowsy,” says Steven Park, M.D., author of Sleep, Interrupted.

3. Watch your caffeine and alcohol habits.

Don’t have any caffeine after 2:30 P.M. (including caffeinated tea and soda), and avoid sipping alcohol three hours before bedtime. Booze may knock you out at first, but it keeps you from getting deep sleep, says Breus. As the sleep-inducing powers wear off, you may even wake up.

4. Experiment with exactly how much sleep you really need.

According to the National Sleep Foundation, some women require as many as nine hours of sleep a night. If you’re snoozing seven and a half hours and still can’t wake up without your alarm, you need more. Try hitting the sack 15 minutes earlier each night until you reach the perfect time for you—it may take a week or so before you reach your own ideal sleep number.

What Might Go Wrong (and How to Fix It)

Sleeping more sounds easy, but it can be hard. Here’s how our testers conquered their biggest hurdles:

“I missed my TV! Going to bed at 9:30 meant I had to skip my favorite shows.” —Johnson

TiVo them, recommends Dr. Lamm. “Even if you do have to totally give up an hour or so of TV, think in terms of what you’re getting in return—a better and healthier body.” Says Johnson, “To tell you the truth, once I got out of the habit of seeing those shows every week, they just became less important to my life.”

“Falling asleep before 11:00 was really hard at first. It didn’t seem right to go to bed so early.” —Hamilton-Romeo

Breus advises that night owls like Hamilton-Romeo switch to the new time line slowly, then stick to it. “I just had to let go of the idea that I needed to do everything,” says Hamilton-Romeo. “Once I actually started going to sleep earlier, I felt so amazing, I wondered why I’d never done it before!”

“I thought I couldn’t survive the day without my afternoon coffee fix.” —Johnson

If you’re a die-hard coffee addict, cutting yourself off at 2:30 P.M. may seem cruel and unnecessary, but trust the experts here—caffeine does affect your sleep in subtle ways, even if you can’t feel it. “If you’re struggling in the first few weeks to give up coffee,” says Breus, “try weaning yourself off slowly with a cup that’s half regular and half decaf, then go all the way.”

“I wondered at first how I was going to find time to spend with my husband when I had to be in bed so early and fit in a ‘bedtime ritual.’” —Braverman

This is a biggie for any woman with a live-in partner or children, says Dr. Lamm. His recommendation: “Ask your partner to get in on the routine with you. It can be sex, it can be cuddling and reading, it can be a warm shower. If that’s the only hour you guys get to spend together, chances are he’ll be willing to skip an hour of TV in favor of some quality time with you.” That’s exactly what Braverman did. Just a few weeks into the makeover, her husband actually started doing yoga stretches with her before bed. “He loves it now!” she says.

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