By Bahram Dideban, MD
“Fat burner” is a loaded term. Technically speaking, a fat burner is a substance that helps the body shed unwanted fat. In health and fitness vernacular, however, a fat burner has come to be known as anything that can aid in weight loss, whether it increases fat metabolism or not.
With this widening definition over the past few decades, a slew of ill-defined products have emerged that hope to capitalize on the supplement market’s unregulated nature. In 2001 alone, the retail sale of weight-loss supplements was over $1.3 billion USD, while a multi-state survey found that seven per cent of the United States’ adult population used an over-the-counter (OTC) weight-loss product.
One benefit of this enlarging market is that since weight-loss supplements now encompass multiple categories it’s become easier to analyze them according to their active ingredients and their purported function. What categories of weight-loss supplements exist? Let’s take a look.
Increase Energy Expenditure
Ephedra and Caffeine
Arguably the most popular category of fat burners are the thermogenics. These are products that attempt to ramp up the natural processes of the body to burn off excess calories as heat. Some of these products may also have direct effects on fat oxidation and metabolism.
The most infamous thermogenic is ephedra or ma huang, a small, twiggy shrub native to Asia. The active components of ephedra, known as ephedrine alkaloids, are commonly available in OTC cold and allergy medications. Ephedrine may decrease body fat by two mechanisms: suppression of appetite and stimulation of energy expenditure (ie. burning off calories as heat).
Ephedrine alkaloids are sympathetic nervous system (SNS) stimulants, with the ability to release adrenaline and noradrenaline into the bloodstream. This increase in adrenaline and noradrenaline levels in turn liberates fatty acids from adipose tissue and intramuscular stores, leading to their breakdown. Similarly, caffeine is an SNS activator, but it also functions to directly increase fat metabolism through a different pathway.
Ephedra, separately and in combination with caffeine, has been the subject of intense research because of its effectiveness but also its major safety concerns. To address these concerns, a literary review of all studies conducted to date regarding the use of ephedrine-containing supplements was conducted by the Southern California Evidence-Based Practice Center (SCEPC).
The literary review, which was called for by the U.S. Department of Health and Human Services, found that over the short term (four to six months) moderate weight loss of about two pounds per month was possible with the use of ephedrine-caffeine combinations. No studies exist that track this weight loss for longer than six months. The major concern, however, was the increased risk of catastrophic events, including five cases of death, 11 cases of stroke, and five cases of heart attack, among others, in previously healthy individuals linked directly to the use of ephedrine-containing products. In response to accumulating evidence of adverse events and deaths, the U.S. Food and Drug Administration (FDA) banned ephedra-containing supplements in 2004.
The effects of caffeine as a supplement have also been studied. In an American Journal of Clinical Nutrition study, lean and obese subjects who were given a 100-mg dose of caffeine had a three to four per cent increase in their basal metabolic rate (BMR) over the following 150 minutes. When the dose was repeated at two-hour intervals over 12 hours, the increase in BMR was even higher, at eight to 11 per cent.
So acute caffeine ingestion has the potential to enhance metabolism, though studies show this effect may be as short-lived as two to three weeks since caffeine tolerance is built up relatively quickly. If supplementation with caffeine is the right option for you, it’s possible to augment this tolerance by taking a complete break from caffeine consumption for one or two weeks and restarting the supplement afterwards.
Increase Fat Oxidation/Reduce Fat Synthesis
L-carnitine, Green Tea Extract, Conjugated Linoleic Acid (CLA)
Carnitine is a vitamin-like substance present in meats and dairy products. Enough carnitine is produced by the human body to maintain muscle, especially the skeletal and heart varieties; therefore, external supplementation is not typically needed. In muscle cells, carnitine plays an important role in fat metabolism, where it functions to transport long-chain fatty acids to their final breakdown site in the mitochondria.
The theoretical basis behind carnitine as a weight-loss aid lies in the assumption that supplementation might increase the levels of carnitine in muscles. This increase, if possible, is thought to result in more fatty-acid transport and, ultimately, breakdown. Carefully conducted studies, however, show that external supplementation does not actually increase the levels of muscle carnitine once sufficient amounts are already present inside the muscle cells. Other trials also found no support for carnitine as a weightloss aid. This means that if you’re not deficient in carnitine, supplementation will do little to help you in your weight-loss goals.
Tea is a familiar product and commonly found in weight-loss supplements due to its ancient roots in health and healing and its popularity as a beverage. Green tea is made from non-oxidized/non-fermented leaves so it retains the highest quantity of pharmacologically active compounds, namely epigallocatechin-3-gallate (EGCG), a catechin polyphenol. Green tea extract (GTE) is the most popular supplement made from tea.
Catechins, specifically EGCG, are thought to stimulate fat oxidation in a similar manner to caffeine, by stimulating the SNS and releasing adrenaline and noradrenaline into the bloodstream. The research on green tea as a weight-loss aid is abundant, but at times conflicting.
The most robust studies have shown that subjects who consumed 120 to 270 mg of GTE combined with up to 50 mg of caffeine had higher rates of fat oxidation. These studies were conducted over a 24-hour period, but longer studies also showed this fat-oxidation effect over eight to 12 weeks, especially during bouts of moderate- intensity exercise. Overall, green tea and GTE are safe for consumption as dietary aids; the American Association of Family Physicians suggests fewer than five cups per day seems to work best for highly active athletes.
Conjugated linoleic acids (CLA) are fatty acids similar in structure to omega-6s. They have been postulated to act as anti-obesity agents with the ability to decrease food intake, decrease fat production by the body, and aid in adipose tissue breakdown.
While studies in rats showed evidence for CLA’s ability to cause weight loss, subsequent human studies do not support that conclusion. A meta-analysis of 18 studies showed that CLA was not able to reduce body weight over the short term. There is some evidence that very long-term supplementation of over three grams per day could cause modest fat loss, but more studies, especially in humans, are needed.
Carbohydrate Metabolism Modulators
Chromium and Ginseng
Chromium is a trace essential element present in foods such as brewer’s yeast, American cheese, mushrooms, and wheat germ. Although the Food and Nutrition Board agreed on an adequate daily chromium intake level of 20 to 30 mcg per day, an American Journal of Clinical Nutrition paper concluded that most Americans are not ingesting even 1/1,000 of that amount.
Chromium deficiency can mimic metabolic syndrome and cause high blood sugar, insulin, and blood triglyceride levels, and low levels of the good cholesterol, HDL. For these reasons, chromium was thought to play a role in carbohydrate and fat metabolism, but all the recent supplementation studies have not only been inconclusive but may also point to serious, potential harms.
Most chromium-based weight-loss supplements use daily dosages of 200 to 400 mcg of chromium picolinate. However, three randomized control trials failed to show any difference in weight loss between the treatment and placebo group. There were also concerns about possible kidney damage and rhabdomyolysis, as well as a theoretical concern that chromium picolinate may lead to free-radical damage. Due to these concerns and a lack of real benefit, an American Family Physician study warns against recommending chromium as a weightloss supplement.
Ginseng, a perennial plant typical of cooler climates like North America and eastern Asia, is a source of ginsenosides, chemicals under investigation for potential use in medicine. Early studies showed a possible correlation between ginseng supplementation and reduced blood sugar and body weight in diabetics, but more robust randomized control trials since then have found no support for ginseng as a weight-loss aid.
Glucomannan, Psyllium, and Guar Gum
Of all the weight-loss supplements, anorectics are the most intuitive. The idea behind them is that the soluble or insoluble fibre they contain can absorb water in the gut but remain undigested, theoretically keeping you satisfied for longer periods of time. The longer you feel full, the less food you eat, and the more weight you may lose. Soluble fibres are also undigested but can be absorbed by the body and may improve or protect against illnesses like diabetes and heart disease.
The trouble is, life is not always so simple. Despite their beneficial role in diseases, 11 randomized control trials using guar gum and a study of 125 diabetic patients using psyllium fibre failed to show any significant weight loss versus a placebo. Three randomized control trials studying glucomannan in dosages of three to four grams per day, however, showed that moderate weight loss (approximately 5.5 pounds in one study) was possible over the course of eight weeks. The researchers also noted a reduction in the bad cholesterol of the blood, LDL, as well as no significant side effects.
Who Could Benefit From Weight-Loss Supplements?
Although the greatest use of OTC weight-loss aids was noted in young obese women (28 per cent), there’s no doubt that fat burners have a firm hold on the fitness industry as a whole. While the goal of the general gym-goer may be to shed the pounds for the sake of health, image, or well-being, the fitness professional is out to achieve an entirely different goal: to succeed in competition. This prompts many fitness fanatics to go above the recommended dose of a product or explore uncharted territory in the pursuit of perfection.
It’s important to remember that there is still no magic bullet for weight loss. The supplements that do have support for their effectiveness and are deemed safe to use would still be best taken under the supervision of a healthcare practitioner. If you feel that weight-loss supplements are the right option for you, concentrate your efforts on those with the largest body of evidence. Combined with the right diet and exercise program, your ideal body may be closer than you think.