Snooki recently lost 42 pounds, but I don't think she used this diet...

The hottest new diet involves eating everything in sight for five days then almost nothing for two. It's a diet that lets you lose weight while eating ENTIRE PIZZAS and TUBS OF ICE CREAM.

The diet comes from a book called "The Fast Diet". It was published in January in England, and it's been the top bestseller there ever since. The U.S. version just went on sale. It seems pretty simple. You eat whatever you want five days a week. The other two days a week, you barely eat ANYTHING. Less than 600 calories for the entire day. Dr. Michael Mosely is the author of the book. He says it's healthy and it works, because switching from heavy eating to fasting immediately takes your body into hardcore fat burning mode. --Mosley tested the diet on himself and lost 20 pounds in nine weeks. His cholesterol and overall body fat level also went down. He says that lowers the risk of cancer and heart disease.

Of course, like all fad diets, it doesn't SOUND like it's a good, safe, or healthy way to lose weight. The National Health System in Britain issued a warning saying, quote, "there is a great deal of uncertainty about intermittent fasting with significant gaps in the evidence." But we all said that about Atkins 15 years ago, and since then, we've learned that carbs really ARE worse for you than bun-less triple-bacon cheeseburgers. So maybe Mosley is ahead of the curve?

Here's the Green Coffee Extract diet we mentioned a couple weeks ago. It's another fad diet used by the Hollywood stars.

Green coffee extract contains fat-busting chlorogenic acids. Demi Moore, Katy Perry and J-Lo are rumoured to use them. According to some nutritionists, the pills can have unpleasant side-effects. A University of Scranton study showed they can boost fat loss by 10%. The pill, sold under the trade name Verdesse in the UK, is made from unripe coffee bean extract, and contains no caffeine - unlike green tea. Instead, the beans contain chlorogenic acids, including one that happens to be a potent natural fat-buster called 5-caffeoylquinic acid.