By Eric Steinmehl
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The sales pitches are irresistible: "Lose 2 Pounds a Day!" "Burn Fat Round the Clock!" "Learn the Amazing Weight-Loss Secret of Hollywood's Sex Symbols!" OK, maybe that's pushing it. But if diet pills could give you Eva Longoria's body, would you bother with the salads and stair-climbing?
Truth is, lifestyle changes are the key to healthy weight loss. Without them, you won't get anywhere. But the six diet-pill ingredients listed here just might help, according to experts at Georgetown University, the University of Mississippi and the University of California, Los Angeles. Want to try one? Check labels to see whether they contain these ingredients, avoid "proprietary blends" that don't reveal their contents, and discuss your weight-loss game plan with your doctor.
What it is: The wake-you-up chemical in your coffee appears to be the most effective weight-loss ingredient. (Health.com: Your vitamin cheat sheet. )
Why try it: A stimulant, caffeine speeds up metabolism and can ward off listlessness from dieting. It may suppress appetite, too, and boost the power of other weight-loss ingredients.
Why not: More than 400 milligrams per day (equivalent to three to four cups of coffee) won't help you lose more weight and could bring on jitteriness, headaches, and insomnia. Unfortunately, most products don't reveal their caffeine quantities in easy-to-understand terms; a typical daily dosage of some supplements might have as much caffeine as 30 cans of Coke (1,200-plus milligrams). Skip it if you have high blood pressure or heart disease, or if you're pregnant or nursing.
What it is: It's green tea's main antioxidant -- the same stuff that may protect against cancer and heart disease -- and is available in green tea supplements. The effective dosage seems to be 90-plus milligrams per day. Or just drink four cups of green tea. Vitamins with EGCG typically don't contain enough of the antioxidant to be useful.
Why try it: EGCG appears to work synergistically with the caffeine in green tea to boost metabolism. And a few small studies suggest it'll help you burn about 4 percent more calories (about 80) a day and specifically burn fat.
Why not: EGCG has no risks, but the caffeine in green tea may lead to jitters if you drink coffee or take a caffeine supplement, too.
What it is: Your body needs this mineral for the hormone insulin (which lets cells turn sugar into fuel) to work effectively. Insulin resistance, linked to diabetes, is thought to make you fat. The effective dosage seems to be 200 micrograms per day.
Why try it: Chromium seems to slightly limit weight gain in people with diabetes or pre-diabetes. And in one study, people who didn't have insulin trouble lost about three pounds more in 10 weeks using chromium than those who didn't. But experts say the mineral may be most useful for people with insulin resistance.
Why not: Years ago, there were health concerns about one form: chromium picolinate. Later studies found it to be safe, though, says Adriane Fugh-Berman, M.D., associate professor in the complementary and alternative medicine master's program at Georgetown. But case reports have linked chronic use of 600 micrograms or more per day to kidney and muscle damage. (Health.com: A guide to today's hot diets. )
Conjugated Linoleic Acid (CLA)
What it is: This fatty acid is a natural substance found in meat and dairy products. The effective dosage used in studies is 3,000 milligrams per day; most supplements contain 1,000 to 1,200 milli-grams per pill.
Why try it: In one trial, women lost 9 percent of their body fat in a year -- and gained muscle, too. In another study, men and women lost about 6 percent of their fat after 6 months. Losing fat can make weight maintenance easier, because you burn more calories when you have less of it.
Why not: CLA may raise cholesterol and worsen insulin resistance.
What it is: Sometimes called Griffonia simplicifolia, 5-hydroxytryptophan is an amino acid that your body eventually converts into serotonin, the brain chemical thought to be lacking in people with depression. It's shown promise as a natural antidepressant. The usual dosage: 100 milligrams, three times a day.
Why try it: 5-HTP may increase levels of a hormone that tells your brain when you're full.
Why not: If you're also taking antidepressants or migraine drugs called triptans, 5-HTP may overstimulate your nervous system and lead to muscle spasms or tremors.
L-dopa or L-tyrosine
What it is: Your body turns the amino acid L-tyrosine into L-dopa and then turns L-dopa into dopamine, another brain chemical linked to cravings and pleasure. A common daily dosage is 500 milligrams.
Why try it: Low dopamine levels may lead to overeating, says John Williamson, Ph.D., of the National Center for Natural Products Research at the University of Mississippi. And researchers discovered years ago that Parkinson's disease patients given L-dopa lost weight. What's more, L-dopa may trigger production of human growth hormone, which builds muscle and reduces fat.
Why not: Some people experience nervousness, heart palpitations and tremors after even low doses.
What not to buy
Cascara: This is a natural laxative -- not a safe way to shed pounds.
Dandelion: It's a natural diuretic, so you lose only water weight.
Ephedra: The Food and Drug Administration banned it in 2004; now, court challenges hope to put it back on the shelf. Ephedra increases the risk of heart problems and stroke.
Garcinia: There are possible links to liver damage.
Hoodia There's been lots of hype about hoodia gordonni, a cactuslike South African plant with appetite-suppressing chemicals (in one study, people who took it ate 1,000 fewer calories a day).
But the hoodia in that test isn't available right now, says University of California, Los Angeles, expert and Health Advisory Board member David Heber, M.D., Ph.D. He says the hoodia products in stores or online probably contain other hoodia types that don't work -- or none at all.
The British company Phytopharm, which has a global patent on hoodia for weight loss, says real products are years away. Bottom line: The available hoodia products may be safe, but they're useless. (Health.com: Find your healthy weight. )
Usnic acid: Found in some bodybuilders' formulas, it's been linked to severe liver damage.