MIAMI -- Wouldn't it be nice if peeling off pounds were as easy as popping a pill?

It's a prospect that raises new hope with every new supplement to hit the market. Among the products being talked about in health and fitness magazines is something called pyruvate. It's just the latest in a long list of so-called slimming supplements that may or may not do as they promise.

We all know that diet and exercise are the keys to getting fit and healthy, but even fitness buffs are easily lured by supplements promising enhanced performance and weight loss.

Pyruvate is the latest dietary supplement making claims to increase fat and weight loss while also improving performance.

"Marketers are very clever," said Rob Herzog, an exercise physiologist at Memorial West Fitness Center. "They'll pick up some small piece of a study, create a product, market it and sell it -- maybe not based on the whole truth."

In the case of pyruvate, studies showed that people did lose weight and fat on the supplement -- but critics say that those losses were minimal and the dosage of pyruvate was considerably higher than what's recommended in supplement form.

"All the studies that were done were done with extremely obese people and the dosage was about 40 to 50 times what's being sold in the stores now -- so whether it would work for the general population in the smaller amounts is not known yet," said Andrea Morgenstein, a registered dietician at Memorial West Hospital.

Safety is another issue. Pyruvate supplements may contain other ingredients, including herbal diuretics.

Every brand is going to be a different composition. You don't know because there's no FDA regulation.

There are some slimming supplements that may really work, but each carries a word of caution.

Several recent studies have suggested that calcium can block fat, but consuming too much can lead to constipation, nausea and even kidney stones.

A dietary supplement called conjugated linoleic acid, or CLA, is also touted as a fat zapper and muscle builder.

While research into CLA is promising, experts say that the dosage should be limited to three grams a day for no more than six months.

The benefits of both supplements were enhanced by, you guessed it, a low calorie diet and exercise. It seems that there's no escape from the inevitable.

Experts say that not only don't some slimming supplements work -- they can be downright dangerous. Among them, Chitosan, which can block the body's absorption of vitamins A, D and K and Ephedra or Ma Huang, which can cause heart attacks, strokes, even death.

Click here to learn about the supplements that contain Ephedra and the possible side effects associated with each.