WebMD Ask the Pharmacist

Rapid Weight Loss

Lose 10 Pounds in 10 Days!

Eat as Much as You Want -- and Still Lose Weight!

Drop One Dress Size a Day!

Rapid weight loss can be quick and easy -- if you believe the advertising claims.

Fad diets and weight loss supplements promise a slimmer body in no time. And Americans want to believe those claims, spending $33 billion every year on weight loss products.

Do any of these products really produce rapid weight loss? Are they safe? And what are the risks of such fast weight loss? WebMD took a look at some rapid weight loss claims, as well as the available evidence.

Rapid Weight Loss: What Is It?

So many marketers promise "fast weight loss" it's difficult to sort through them all.

Most rapid weight loss pitches fall into these categories:

Starvation Diets

Beyonce popularized the so-called "master cleanse" diet: water, lemon juice, maple syrup, and cayenne pepper. Variations of these diets have been around since at least the 1950s. They often also promise "detoxification" through colonics or enemas.

Diet Pills and Supplements

Dozens of diet supplements promise to speed weight loss. Generally, they claim either to block absorption of nutrients, increase metabolism, or burn fat.

Very Low-Calorie Diets (VLCDs)

These medically supervised diets often take place in a specialized setting away from temptation. (Sometimes these places are referred to as "fat farms.") For weeks, dieters eat only about half their daily calorie requirement. VLCDs are expensive, difficult -- and often effective.

Creams, Devices, and Magic Voodoo Spells

There seems to be no end to the dubious ideas promoted in the name of rapid weight loss. Most promise to replace diet or exercise.

Does Rapid Weight Loss Work?

The FDA does not regulate over-the-counter weight loss products. Marketers make their claims freely, usually with no research or proof that their products work.

The only proven method of safe, rapid weight loss is the medically supervised very low-calorie diet (VLCD). Most of what is known about rapid weight loss comes from studies of people on these diets.

No other product, pill, or diet has been proven to work for fast weight loss. The FDA-approved medicines Xenical and Meridia can help, but they work slowly and only with diet and exercise.

The FDA has announced that it is reviewing adverse event reports of liver injury in patients taking Xenical  and the over-the-counter drug Alli.

In any rapid weight loss program, what really burns fat is not a pill or type of food. It's the drastic reduction of calories, combined with exercise.