More than half of the adults in the US consume dietary supplements. About one out of four of us who take supplements are taking them for weight loss. Almost one in ten normal weight women are taking supplements to try to avoid gaining weight, and nearly one third of overweight women take them to lose weight. Many people assume that dietary supplements are natural, and therefore are safe to take. But the world of supplements is still the Wild West, with nobody enforcing law and order. If you venture there, you do it at some peril. The Food and Drug Administration must prove that a dietary supplement causes an “unreasonable risk of illness or injury” before it can remove the supplement from the market. A consequence of the lack of regulation over the manufacture and distribution of dietary supplements is that you can never be sure what you are actually taking. The amount of active ingredient in supplements varies from an undetectable amount to more than three times the amount that is listed on the label. Even more worrisome are the ingredients that the label doesn’t mention. In 2008 the FDA warned people to not take more than 25 different weight loss products because they contained substances not on the label, such as the prescription drugs sibutramine (which is a prescription weight-loss drug, now off the market), rimonabant (a weight loss drug not approved in the US due to concerns about safety), phenytoin (a seizure medication that is dangerous in high doses), and phenolthalein (a suspected cancer causing chemical that is not usually used in food). The doses of these drugs found in the supplements was often much higher than safe prescription doses. Although the supplements contained these drugs, they were often labeled as “natural” or containing only “herbal” ingredients. In 2009 the FDA found many more supplements that contained a wide variety of unlabeled ingredients. In addition to the drugs listed above, some contained furosemide (a diuretic “water-pill” that can cause dehydration and low potassium). Some ingredients, like St. John’s wort (an antidepressant herb with no benefit for weight loss) or sedatives (chemically related to Valium, that can cause addiction) are added, not to help with weight loss, but to hide the side effects of stimulants (which can cause high blood pressure and rapid heart rate). Though the FDA identified more than 140 contaminated supplements, these likely are only a small fraction of the contaminated products on the market. In order to make it harder to find the undeclared ingredients in supplements, some manufacturers have changed the chemical structure of the drugs. But when you change the chemical structure of a drug, you change how it works in your body. Since these modified chemicals have never been studied in humans, we don’t know if they work or are safe to use. And what benefit are you likely to get for taking these risks when you take a weight loss supplement? A systematic review of all double blind randomized controlled trials of dietary supplements for weight loss concluded that there is no good evidence that any of them work. There are no supplements for weight loss that have been proven to be safe and effective. If there ever is a product that is truly safe and effective, we won’t know that it is both safe and effective until it has been available for quite a long time, and by then you will already have heard about it unless you live in a cave somewhere. Any easy, safe, effective weight loss supplement will become a certain blockbuster best seller. But until then, be skeptical. If it sounds too good to be true, it is. You are probably going to be healthier and just as thin if you avoid all the weight loss supplements that are currently available. Prescription Medications Medications to treat obesity fall into three broad categories. Some medications try to decrease food intake by reducing hunger or prolonging feelings of fullness. Others work by decreasing the absorption of calories from our digestive tract. The third way is to speed up our metabolism so we burn up more calories without exercising more. No currently available medications work very well. And weight loss medications generally have a very poor track record for safety. Though medications can help people to lose some extra weight in the first few months, people do not continue to lose weight. And when they stop taking the medications, they gain the weight back again. Just like for over-the-counter medications, any safe and effective prescription weight loss medication is sure to be a multi-billion dollar a year best seller. The most recent candidate for effective weight loss was the combination of phentermine and fenfluramine (Phen-Fen) that was very popular until people started getting damaged heart valves and permanently increased blood pressure in the lungs. There are only a handful of prescription medications that have been approved by the Food and Drug Administration (FDA) for weight loss, and none of these is approved for use longer than 2 years. A review of all the randomized clinical trials of prescription medications for obesity found that they help people to lose between 4 ½ pounds and 11 pounds of extra weight more than they would lose by diet and exercise alone. This weight is usually lost in the first six months, and extra weight loss after 6 months with these medications is unlikely. When people stop taking them the medications, they tend to gain all the weight back. None of the medications have been studied for use in children and adolescents. The National Institutes of Health recommends trying to lose weight for at least 6 months before considering taking a medication for weight loss. You should continue lifestyle changes of diet and exercise to help you to lose weight even while you are taking a weight loss medication. Someday we may have a safe and effective medication or supplement for weight loss. When that day comes, we will all know about it because the treatment will be all over the news and talk shows and your physician will happily be recommending it to you. This is not that day.