5 Ways to Crash Diet—what's new, what's safe

Cabbage soup, anyone? Master cleanse? How about the air diet?

When news broke that Prahlad Jani, an Indian yogi, was claiming to have eaten nothing for the last 70 years, I thought, well, there's an idea.

Seriously, though, the crash diet has gone way out of style; in fact, it has been considered a kind of medical no-no. So with Memorial Day upon us, and bikini-season less than a month away, what's a time-challenged (did someone say, panicked?) woman with a few extra pounds to do?

Here's the latest spin on speed-dieting:

Make it the Start: Medical types hate crash diets because they're short-lived. Fair enough. But a quick-weight drop might be just what the doctor ordered in terms of inspiring you to go the distance. "My research, and that of others, shows that people are more likely to lose weight long term if they have early success," says Kelly Webber, PhD, assistant professor at the University of Kentucky and coauthor of two new studies on motivation. Because dieters' gung-ho tends to droop at about four weeks, she says, "having support is critical to keep you going, whether it's a dietician or a friend."

The fast route? "It's just nonsense," says Frank Greenway, MD, when I ask him about the Indian yogi. "Physically impossible." Greenway, a weight specialist who heads the oupatient clinic at Pennington Biomedical Research Center in Louisiana, goes on to say that a real fast can backfire: Studies have shown that after six weeks or so, the starving body-desperate for glucose-starts to eat up its own lean muscle (think "heart"). In the 1970s, in fact, several women died from cardiac arrythmias after doing the Last Chance Diet, a 400 calorie-a-day liquid protein concoction. "That put the whole field in a dither," he says.

So how low-cal should you go? Rock bottom: 800 calories a day-but only under a doctor's care. For the average-sized healthy women, Greenway says, don't go below 1200 calories. Most nutritionist agree.

Extra Cred: That 1200 number, by the way, easily counts as "caloric restriction" (CR)-the idea that slashing one's food energy (by, say, 25 percent) will keep you younger and living longer. If there's something a little eerie about the sinewy members of the CR Society, who are devoted to this lifestyle, they seem onto something. Research on animals is quite promising, and the first results on humans show that after six months, people who reduced their calories between 10 and 30 percent have enhanced T-cell function. "Although our data is preliminary," says study researcher Simin Nikbin Meydani, PhD, a professor of nutrition and immunology at Tufts University, "it suggests that CR could make a person more resistant to infections."

Key Nutrients: Where your 1200 calories come from is crucial. Greenway suggests a diet that's around 20 percent fat-you need at least that much not to go crazy with hunger. The rest should be about 60 percent carbohydrate and 20 percent protein. It goes without saying that "fat" here means olive and fish oil versus butter and trans fat, while "carbohydrate" refers to whole grains, fruits, and vegetables. As for protein, it's important to get premium quality. "Egg whites are the closest to what people need," says Greenway. (One large white has about 3.60 grams of protein and a 140 pound women requires about 50 grams per day.) "Milk and soy are also good sources."

Get off the Yo-Yo: Remember, this is the beginning. If you "crash diet" as in "crash test dummy," you'll only end up like a wreck, gaining the weight back. If your "crash" is about bursting out of the gate to get a head start on the long haul, you're off to a great summer-and beyond.

Are you raring to lose weight for the beach?

For more on "the good, the bad, and the healthy" of dieting...

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[photo credit: Getty Images/photodisc]