Weight loss and muscle building supplements

Tribulus Terrestris
Derived from the puncturevine plant, this supplement is sold alone or as a key ingredient in many so-called testosterone boosters. Prices vary; you can buy a 12-pack of Tribulus Shot liquid supplement for $24, or plunk down $65 for 60 capsules of Sylvester Stallone's Instone Forza-T. Marketers claim that Tribulus terrestris boosts testosterone production and therefore increases muscle mass and strength (not to mention libido). However, a four-week study of 21 healthy young men reported in the Journal of Ethnopharmacology failed to find any measurable differences in testosterone levels between those taking the supplement and a placebo group.

Bottom line: Keep your cash. Taking this herbal supplement could lower good cholesterol and cause breast enlargement, says Mark Moyad, M.D., Phil F. Jenkins director of preventive and alternative medicine at the University of Michigan Medical Center.
Click here for your A to Z guide on all supplements: The Men's Health Supplement Guide

DHEA
As the only prohormone not affected by the 2005 FDA ban, DHEA has been making a comeback. But DHEA survived the ban thanks to aggressive lobbying efforts, not for reasons of safety or effectiveness, says Dr. Moyad. Secreted by the adrenal glands, this hormone can be converted into testosterone and estrogen. Levels peak in your twenties and then decline with age, which explains its appeal to men in midlife. Supporters claim DHEA slows signs of aging, including muscle loss. However, a recent study of DHEA in the New England Journal of Medicine failed to find any of the benefits men expect from a muscle booster. The two-year study followed 87 men and 57 women ages 60 and older who had low DHEA levels. Although supplements did raise DHEA levels to normal, researchers found no significant changes in muscle strength or body composition.

Bottom line: Skip it. DHEA reduces good cholesterol, so it's not a heart-healthy choice. Plus, there's the unwanted side effect of extra estrogen and the dreaded "man boobs." A better idea: Get your testosterone levels checked by your doctor, who can prescribe the hormone if your levels are low.

ATHLETIC PERFORMANCE

Whether you want to work out harder, lift longer, or recover faster, you'll find a variety of supplements that promise to help you do just that. (With or without supplements, our new cutting-edge DVD fitness program Speed Shred will help you torch calories and build rock-hard muscle.)

Creatine
One of the most popular nutritional supplements of all time, creatine is used to fuel energy in the muscles, primarily for high-intensity, short-duration exercise such as sprinting and lifting weights. It may help you work out harder and longer, and recover faster. And when used during resistance training, creatine has been shown to increase total body and lean body mass. Of the 300 or so studies that have investigated creatine for its ability to enhance athletic performance, about 70 percent have found statistically significant gains.

Bottom line: We recommend it. Understand, though, that muscle cramping and stress injuries are commonly reported side effects.