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As everyone on the planet probably knows, Americans have a weight problem. In fact, 69 percent of adults are overweight and 35 percent qualify as obese.

Consumers spend billions annually in a desperate search for a solution. The problem is that with weight loss — as with most health problems — there’s no magic bullet.

Weight-loss supplements

About 1 in 4 Americans have used weight-loss supplements, and half of supplement consumers have taken them in the past year, according to a nationally representative sample of 2,966 Americans conducted by Consumer Reports. About half of those users reported at least one side effect, most often a faster heart rate, jitters, digestive problems or dry mouth.

But unlike drugs, which must be proved safe and effective before being marketed, supplements are assumed to be safe unless proved otherwise. The Food and Drug Administration has recalled hundreds of weight-loss supplements containing ingredients that were rarely listed on the labels. In 2013, 72 cases of severe hepatitis and liver failure (including one that led to a death) were linked to OxyElite Pro, a weight-loss supplement.

The stimulant 1,3-dimethylbutylamine (DMBA), which has never been studied in humans, was recently detected in the widely sold weight-loss supplements MD2 Meltdown and OxyTherm Pro, among others. The health risks of DMBA aren’t fully known, but it’s chemically related to DMAA, a stimulant that the FDA has barred supplement makers from using because it can lead to elevated blood pressure and cardiovascular problems.

The word “natural” on a label is no guarantee of safety, although about one-third of the supplement users in the survey thought that it meant the product was safer than prescription medication.

Consumer Reports’ take: Don’t take weight-loss supplements. They’re mostly unregulated, they probably don’t work, and they could harm you.

Prescription diet pills

Four weight-loss medications are available to consumers. But they’re only for people with a body-mass index of 30 or greater, or those with a BMI of 27 and a weight-related health condition. Here’s a rundown:

Alli/Xenical (orlistat): In both of its forms — over-the-counter (Alli) and prescription (Xenical) — orlistat works by blocking the enzyme that allows you to digest and absorb dietary fat.

After a voluntary recall last March (the manufacturer suspected tampering after consumers reported bottles containing tablets in various shapes and colors), Alli is expected to return to stores in the first half of 2015.

In clinical trials, severely overweight patients who were put on a reduced-calorie diet lost seven pounds more after a year of treatment with orlistat than those who took a placebo. Orlistat has been linked, on rare occasions, to severe liver damage, liver failure (resulting in a transplant) and even death. Last summer, the manufacturer added a warning to the label, noting that the drug might interfere with the absorption of anti-seizure and other medications. Orlistat may decrease the absorption of vitamins A, D, E and K. Other side effects include gas and involuntary discharge of stool.

Belviq (lorcaserin): This medication promotes weight loss by activating brain receptors for serotonin, a neurotransmitter that triggers feelings of fullness. After a year, those taking it lost only six pounds more than those who took a placebo. After another year, participants gained back about a quarter of the weight they had lost. They also had trouble staying on the drug; side effects include headaches, dizziness, fatigue, nausea, constipation, memory and attention problems and (rarely) a leaky heart valve. As a result, the FDA has mandated studies to rule out heart problems. Like many prescription drugs, Belviq can interact dangerously with other medications.

Qsymia (phentermine/topiramate): This drug is a combination of two prescription medications — phentermine, a stimulant that suppresses appetite, and topiramate, an anti-seizure drug that sometimes causes weight loss as a side effect. Qsymia leads to more weight loss than the other medications. But it increases heart rate and may lead to memory, attention or speech problems, anxiety, insomnia and depression (including suicidal thoughts). About 40 percent of clinical trial participants stopped taking it. To ensure that it doesn’t cause cardiovascular problems, the FDA has requested a post-market study.

Contrave (naltrexone/bupropion): This combination of naltrexone (an addiction medicine) and bupropion (an antidepressant) may reduce appetite and curb cravings. After a year on the drug, nondiabetic patients in a clinical trial lost 4.1 percent more weight than those who took a placebo. Nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth and diarrhea are the most common side effects. More troubling, the drug may cause seizures. And because it contains bupropion, it must carry a boxed warning saying that it may increase suicidal thoughts and behavior. The FDA is concerned about the medication’s effect on the heart and is requiring more studies.

Consumer Reports’ take: Skip those drugs and stick with calorie reduction and exercise to drop pounds.

Copyright 2014. Consumers Union of United States Inc.

For further guidance, go to www.ConsumerReports.org/Health, where more detailed information, including CR’s ratings of prescription drugs, treatments, hospitals and healthy-living products, is available to subscribers.