Cheap Tricks

By Megan McNamara, additional reporting by Morgan Lord

What you can learn from four crazy diets (besides what not to do).

We all know someone who diets on the fringe: the roommate who pops caffeine pills, the coworker who eats nothing but cottage cheese for a month. Whenever she gets on her latest skinny-by-Sunday kick, we roll our eyes and laugh--until it works.

Though the insta-results of crash diets may tempt you to chuck your food journal and load up on six-packs of Breakstone's, there's a better way. After all, your friend isn't just torturing her taste buds--­research shows that über-restrictive weight-loss plans can lead to fatigue, dehydration, constipation, and diarrhea. Long term, she's raising her risk for gallstones, osteoporosis, and heart damage--not to mention upping the odds of gaining all the weight back.

You, meanwhile, can use her crash diet as a crash course in improving your own. We dissected four extreme diets (ones we'd never actually recommend trying) to find the facts behind the fads. Here's what they can teach you about dropping pounds safely and sanely.

The Fad: Dinner for Breakfast

Belly bulge is more than a nuisance when you bare it onstage twice a week. That's what helped librarian and belly dancer Nicole Sinclair (unlike our other dieters, she didn't want us to use her real name), 36, stomach a diet of steak for breakfast and toast for dinner. "I read that Westerners eat their meals the wrong way around, so I decided to give it a shot," she says.

That meant pasta, casseroles, even lamb stew in the morning; a salad in the afternoon; then tea and fruit in the evening. Sinclair lost 18 pounds in a matter of months as a result. But within the year, she was back to morning toast and her original weight.

Why it worked: "Sinclair gave her body the most calories in the morning, which is when it was prepared to burn more," says Cynthia Sass, M.P.H., R.D., author of Your Diet Is Driving Me Crazy. Most of us are pretty inactive between dinnertime and The Daily Show, so not much is getting worked off. Also, "Sinclair cut portions just by having a less leisurely meal," says Arthur Frank, M.D., medical director of the George Washington University Weight Management Program. By eating her biggest meal before rushing off to work, she had no time (and probably no taste) for appetizers, cocktails, or dessert.

What to steal: Mix up your routine. "Sometimes a life or even a schedule change can jar you out of a rut," Sass says. "I've had clients break overeating patterns thanks to a move, a new job or relationship, or getting a dog." If you aren't due for a major transformation, even a small change can help rewire your eating habits. Try taking a class, pursuing a hobby, or just going for a walk instead of an after-meal sugar rush.