About 15 percent of Americans have used weight loss pills at some point, reports the National Institutes of Health (NIH). Yet less than one-third of them consulted a medical professional beforehand. With a few exceptions, most fat burners carry side effects and may put your health at risk.
If you're looking for safe fat-burning supplements, consult with your doctor first. Even a formula containing natural ingredients may cause adverse reactions.
Potential Risks of Fat Burners
Fat burners are some of the most popular yet controversial weight loss supplements out there. They're widely used by athletes, dieters, fitness models and gym-goers alike. Scientists, though, are questioning their safety and effectiveness.
Some weight loss pills contain more than 90 different ingredients, as the NIH points out. These can interact with each other as well as with other drugs. If you have heart disease, diabetes, liver problems or other conditions, talk with your doctor before using these products. Some ingredients may worsen your symptoms or cause adverse reactions.
Most fat burners contain a mix of stimulants and herbal extracts that claim to increase metabolism, reduce fat absorption or suppress appetite. Bitter orange, for example, is one of the most widely used ingredients in these formulas.
According to an August 2012 review published in the International Journal of Medical Sciences, this compound is rich in p-synephrine, a thermogenic agent that may increase calorie burn, curb hunger and suppress the formation of new fat cells.
However, most studies conducted on bitter orange and its active ingredient were small — with fewer than 40 subjects — and involved the consumption of several other compounds, such as caffeine. Therefore, their results may not be conclusive. Plus, it's hard to say whether the weight loss was due to caffeine, p-synephrine or dieting.
As the researchers note, subjects reported adverse reactions ranging from mild to severe. Ventricular fibrillation, stroke, myocardial infarction and high blood pressure were just a few examples.
Green Tea and Weight Loss
The NIH and other health organizations suggest that some weight loss pills may inhibit appetite, reduce fat absorption and accelerate fat loss. However, they all carry potential side effects. The key is to discover what works best for you. Also, be aware that your diet and exercise habits matter most.
Take green tea extract, for example. This natural compound may cause modest weight loss, but it's unlikely to help you keep the pounds off, according to a research paper featured in the Cochrane Database of Systematic Reviews in December 2012. Caffeine and catechins, its active ingredients, may slightly increase your metabolic rate. Most studies have mixed results, though.
A July 2014 review published in the European Journal of Clinical Nutrition assessed the anti-obesity effects of green tea. Some studies showed that green tea extract may reduce fat mass, waist circumference and body weight, while others didn't report any major improvements.
In most clinical trials, this compound produced better results when used as part of a diet and exercise plan. More research is needed to confirm its efficacy.
Always take green tea extract with food. This compound may affect your liver when ingested on an empty stomach.
Despite its high antioxidant levels, green tea extract isn't entirely safe. Hypertension, digestive distress, nausea and liver dysfunction are all potential side effects, as the NIH points out. Taking this supplement on an empty stomach may increase the risk of liver damage.
Does Caffeine Burn Fat?
A popular ingredient in weight loss pills is caffeine. This compound may support weight loss maintenance, according to another review featured in the European Journal of Clinical Nutrition in April 2016. In clinical trials, subjects who managed to keep the pounds off reported drinking more coffee and caffeinated beverages compared to the control groups.
Furthermore, a January 2016 research paper published in the Journal of Basic and Clinical Physiology and Pharmacology suggests that caffeine may inhibit hunger and increase satiety, making it easier to reduce your food intake.
In one study in the review, food intake was reduced by more than 20 percent in men who ingested this compound. Women didn't experience this effect, though. Caffeine appears to be even more effective for appetite control when combined with red pepper, soluble fiber or green tea catechins.
The same source indicates that caffeine intake may increase energy expenditure due to its thermogenic properties. To put it simply, caffeine elevates core body temperature, leading to more calories burned throughout the day. Again, most studies were small and had conflicting results.
Try not to exceed 3 to 6 milligrams of caffeine per kilogram of body weight, recommends a May 2018 review on caffeine-related deaths published in the scientific journal Nutrients. One cup of brewed coffee has around 95 to 165 milligrams.
Fat burners, on the other hand, are more concentrated. High doses of caffeine may cause life-threatening symptoms and even death.
Like most weight loss supplements, caffeine has its share of side effects, including nausea and vomiting, seizures, rapid heartbeat, poor sleep and jitters. When ingested in large amounts, it can be fatal.
Beware of "Healthy" Fat Burners
As you see, many so-called "healthy" fat burners, such as caffeine and green tea extract, may not be safe. Other common ingredients in weight loss pills carry even greater risks.
Yohimbe, for example, is marketed as a natural fat burner and performance enhancer. However, most claims lack scientific proof. Its side effects, on the other hand, are well-documented.
Taking as little as 20 to 40 milligrams of this compound may increase blood pressure, says the NIH. Doses of 200 milligrams and above may cause rapid heartbeat, headaches, cardiac failure or even death.
Garcinia cambogia, another popular ingredient in diet pills, may affect the liver, trigger inflammation and increase oxidative stress. This compound is extracted from the fruit with the same name and marketed for its anti-obesity effects. Although it appears to be safe when used for short periods, there is still a risk of toxicity.
According to a December 2016 case report featured in the World Journal of Gastroenterology, this supplement may cause liver failure. A 34-year old man who took 80 milligrams of "pure" Garcinia cambogia three times daily experienced gastrointestinal symptoms, such as nausea and stomach pain. He also had dark urine. Six weeks later, he developed new symptoms, including a decline in overall health and mental status.
The patient was diagnosed with hepatic failure and required liver transplantation. As the researchers note, Garcinia cambogia may be responsible for several other cases of acute liver failure that occurred recently.
"Natural" doesn't always mean "safe." Weight loss supplements may contain dozens of natural ingredients that can interact with each other. Some also use proprietary formulas, so you don't really know what's inside the bottle.
Unfortunately, there is no such thing as "safe" fat burning supplements. Any diet pill, whether natural or synthetic, carries potential risks. In fact, 27 percent of the dietary supplements recalled by the FDA between 2004 and 2012 were diet pills, as reported by the NIH. Most products contained hidden ingredients.
No diet pill will help you torch fat overnight. Some formulas have diuretic effects and may reduce fluid retention, but you'll lose water, not fat. Others may slightly increase your metabolism and stimulate fat burning, but only when combined with diet and exercise. Most times, the risks outweigh any potential benefits.
- National Institutes of Health: "Dietary Supplements for Weight Loss"
- Food and Chemical Toxicology: "Risks Associated With Fat Burners: A Toxicological Perspective"
- International Journal of Medical Sciences: "A Review of the Human Clinical Studies Involving Citrus Aurantium (Bitter Orange) Extract and Its Primary Protoalkaloid P-Synephrine"
- Cochrane Database of Systematic Reviews: "Green Tea for Weight Loss and Weight Maintenance in Overweight or Obese Adults"
- European Journal of Clinical Nutrition: "The Anti-Obesity Effects of Green Tea in Human Intervention and Basic Molecular Studies"
- European Journal of Clinical Nutrition: "Caffeine Intake Is Related to Successful Weight Loss Maintenance"
- Journal of Basic and Clinical Physiology and Pharmacology: "The Effect of Caffeine on Energy Balance"
- NCBI: Nutrients: "Caffeine-Related Deaths: Manner of Deaths and Categories at Risk"
- National Institutes of Health: "Garcinia Cambogia"
- Mayo Clinic: "Caffeine Content for Coffee, Tea, Soda and More"
- World Journal of Gastroenterology: "Dangerous Dietary Supplements: Garcinia Cambogia-Associated Hepatic Failure Requiring Transplantation"