Quack Diet Red Flags

Lose that weight -- you know you should. But the sheer numbers of weight loss programs sometimes confuse the issue.

The cabbage diet! The rice diet! The blood type diet! Atkins! South Beach! No carb! Low carb! There's even a Jesus diet (sans loaves and fishes).

"People who want to lose weight are a very vulnerable group because they're very frustrated," Kathleen Zelman, MPH, RD/LD, director of nutrition for the WebMD Weight Loss Clinic, tells WebMD. "Weight loss is hard, and everybody is looking for a silver bullet."

How can you discern which weight loss claims are true or false? Here's some advice from Zelman and from the Federal Trade Commission:

Does the diet promote rapid weight loss?

That's a clear signal it's unrealistic, says Zelman. When you start a diet, water weight is the first to go, she explains. If you lose much more than two pounds a week, you're drawing from both fat and muscles. That's not good, because muscle is one big factor that controls your metabolism. If you lose muscle mass, your metabolism will slow down. That's how the yo-yo cycle begins -- and that's one reason why some diets don't work, she explains.

"That's why we advocate losing weight slowly and gradually, so you're losing one to two pounds per week," Zelman says. "You're eating more food than diets allow, but you're tapping into stored fat more efficiently."

Does the weight loss program involve eating just one food -- or eliminating whole food groups?

"That's crazy," says Zelman. "No one can stay on those diets very long."

Sure, you can do it in the short term -- with some success, she says. "If you're eating all the cabbage or meat you want, you go into a state of ketosis. This causes your appetite to go away, so ultimately you don't eat as much -- probably you're down to a 1,000-calorie diet. Anyone on a 1,000-calorie diet willlose weight.

"Even the strangest diets will pull weight off you, because the basic formula to weight loss is burning more calories than you eat."

Does the program help you change long-term eating habits?

If not, you'll just get caught up in a never-ending lose-gain cycle -- better known as "yo-yo" dieting.

Most diets are short-term fixes for a long-term problem, says Zelman. "People who get slim and stay that way have changed their eating habits and attitudes toward food."