Assessing the science behind weight loss supplements

When it comes to weight, America has a problem. Nearly 27 percent of Americans report that they are obese (based on self-reported weight and height, and defined as a body mass index (BMI) greater than 30), according to data from 2009 (the most recent year available).

Although that number may not seem significant, consider this: Obesity is a risk factor for a number of diseases, including metabolic and cardiovascular diseases, such as Type 2 diabetes, dyslipidemia, atherosclerosis, hypertension and stroke; and for cancer, including cancers of the colon, breast, kidney and digestive tract. It's also a risk factor for nonlife threatening diseases, including arthritis, sleep apnea, gallstones and gout; and for affective disorders, including low self-esteem. With such a laundry list, experts say it is in the public's interest for Americans to lose that excess weight. But the only proven way to do so is to move more, eat less and eat better. In a society where food often is plentiful and where many have sedentary lifestyles, this may be easier said than done.

This is where weight loss pills -- pharmaceutical or over-the-counter dietary supplements -- enter the fray. Our buyer's guide outlines the types, science, efficacy and issues involving the pills, but they all have one thing is common: None of them work on their own, you must diet and exercise as well. There is no magic bullet. All of these are merely tools to help advance weight loss efforts.

Unfortunately, there are plenty of companies who want to prey upon people's desire to both lose weight and for the quick fix. They advertise supplements with claims that have not been verified or tested by a reputable independent organization. Manufacturers don't have to seek FDA approval before putting dietary supplements on the market.

Because diet pills come and go, and because there are some who question whether regulation of dietary supplements is effective, it is impossible for us to choose a Best Reviewed diet pill. Instead, we have assembled the science and safety profiles for each type and gathered specifics on their ingredients. These include pharmaceuticals, nutrient blockers (fat and carb blockers), fat burners, insulin regulators, appetite suppressants and body composition changers.

We turned to the scientific community and government agencies for information. We consulted with publications from the CDC, U.S. Food and Drug Administration, the Natural Medicines Comprehensive Database and medical journals. We also relied on reports from major newspapers, such as The New York Times, Los Angeles Times and The Wall Street Journal, because we found that they presented a fair and balanced review of weight-loss drugs. Website and magazine articles, such as ones from Redbook, and Health, cover these topics briefly, but we found that their coverage is largely superficial. We list them in the sources section, because they are easy to access and provide some overviews and expert opinions.

Types of Diet Pills

  • Some studies show mild weight loss
  • Generally safe when taken at low doses for short periods of time
  • Potential for serious side effects
  • Some are dangerous
  • Can make you feel anxious and jittery
  • Insufficient reliable evidence to recommend their use

Thermogenics don't necessarily burn fat as their marketing name -- fat burners -- suggests, but they work by increasing the amount of energy your body expends while at rest by stimulating the sympathetic nervous system. That's the part of our nervous system responsible for the "fight or flight" response, which increases heart rate and blood pressure. If thermogenics are taken in large amounts or for extended periods, these heart rate and blood pressure increases can have serious side effects, including strokes, irregular heart rhythms and even heart attacks. Science doesn't show that these risks are worth the nominal weight loss that these products may produce, and the risks increase when two or more ingredients are combined. This brings two points of caution when using thermogenics:

1)     Watch out for products that contain multiple ingredients, which can increase your risk of serious side effect.

2)       Be aware of how much of one active ingredient you're taking -- such as caffeine, which is found in guarana and green tea -- so you can avoid an overdose. 

  • Generally safe at low doses for short periods of time
  • Potential to help not just with weight loss but also diabetes
  • Insufficient evidence to recommend
  • Could lower blood sugar too much in diabetics
  • Possible liver damage when taken in large amounts
Insulin regulators work by enhancing the effects of insulin, a hormone involved in carbohydrate and fat metabolism. Chromium and cinnamon don't have sufficient evidence behind them to recommend their use in weight loss; however, each one's side effects are minimal, except when taken in large quantities. Then they could potentially cause liver damage. There is not enough evidence to prove they can help one lose weight, but some studies have found that chromium and cinnamon can lower glucose, diabetics should be cautious before taking either as a supplement.
  • Initial studies look promising
  • Minimal side effects
  • Could keep you from having to completely eliminate carbohydrates
  • Insufficient evidence to recommend
  • Can cause some gastrointestinal upset
Carbohydrate blockers work as their name suggests, blocking the absorption of carbohydrates in the body. White kidney bean extract (Phaseolus vulgaris) decreases the calories absorbed from carbohydrates, so it could potentially allow you to eat carbs while losing weight. Initial studies are promising: Weight loss was mild at 4 to 8 pounds with minimal side effects. Though this isn't enough to recommend this carb blocker for weight loss, white kidney bean extract could potentially have a future as a weapon in fighting flab.
  • Minimal side effects
  • Insufficient weight loss proof
  • Not good for those allergic to shellfish
  • May interfere with medications
Fat blockers work as their name suggests by blocking the absorption of fat in the intestines. Chitosan is one of the more well-known ingredients that perform this function, and it is made from the shells of crustaceans. The lesser known alginate is found in brown algae. Neither has been proven as a weight loss aid. Further research is needed, but if the data continues to come in the way they have in the majority of studies, neither chitosan nor alginate will be recommended for use in weight loss. Also, because they interfere with fat absorption, they can potentially interfere with the absorption of medications. Lastly, chitosan should be avoided if you have an allergy to shellfish.
  • Some have been used for centuries
  • Insufficient evidence to recommend their use
  • Potential serious side effects, such as esophageal or intestinal obstructions and liver damage.
Appetite suppressants curb your hunger; if you eat less, you'll lose weight. However, of the ingredients that we studied, there wasn't sufficient evidence to recommend their use. The most interesting are caralluma and hoodia, which have been used for centuries by indigenous tribesmen to suppress appetite, but further research is needed to see if they can be proven clinically effective. Some appetite suppressants have the potential for serious side effects: Hydroxycitric acid (HCA) has the potential to cause liver damage; glucomannan and guar gum if taken in large amounts and without water can potentially cause esophageal and intestinal obstructions; and the use of 5-hydroxytryptophan (5-HTP) has been associated with a condition that affects blood cells and muscles called eosinophilia myalgia syndrome (EMS). It is recommended that use of 5-HTP be avoided until further research is completed.
  • CLA may live up to claims
  • Minimal side effects when used for the short-term
  • None decrease weight
  • Multiple reports of liver damage with usnic acid
  • Some PS supplements derived from cow brains
Muscle builders or body composition changers are meant to do what their name implies by helping to increase lean body mass and decrease the amount of body fat you have. This recipe will not show up on the scale -- which is probably why there isn’t any scientific evidence supporting their use in weight loss -- but rather in how your body looks and fits in clothes. There is only one ingredient that carries its weight in research literature: conjugated linoleic acid (CLA). It can help to decrease body fat and increase lean body mass. As for other ingredients in this category, their performance is mixed. There is conflicting evidence as to the effectiveness of hydroxymethylbutyrate (HMB) at increasing lean body mass, but there's no evidence supporting the ingredients l-carnitine, usnic acid or phosphatidylserine. While most of the muscle builders have minimal side effects, usnic acid should be avoided because of multiple reports of liver damage. Also the source of phosphatidylserine (PS) should be verified. Most manufacturers use soy and cabbage, but originally PS was mainly derived from cow brains and there was the potential for the transmission of mad cow disease.
  • Used under doctor supervision
  • Overseen by Food and Drug Administration
  • Proven modest weight loss
  • Various side effects
  • Not many choices
  • Can be expensive
Prescription drugs could be the gold standard (if there was one) of the diet pill industry. Regulated by the Food and Drug Administration (FDA), companies are required to prove that their weight loss products either produce weight loss that is greater than 5 percent (compared to people taking a placebo) or help more than 35 percent of the population achieve greater than 5 percent weight loss; in addition, lipid, glycaemia and blood pressure profiles must improve. These requirements have made the options available limited. The few options available are associated with 3 percent to 5 percent loss of bodyweight over six months to one year and improved cardiovascular benchmarks, such as blood pressure.

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