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What are 'fat burners' and do they really work? By Kristin J. Reisinger, MS RD Get fired up! Feel the burn! Burn up to 613% more fat! This is what you're inundated with every time you open up an issue of M&F or MuscleMag. Does this sound too good to be true? Hhmmmm... Anything sounding that good usually is. There's no free lunch in this world so what are the costs of taking these supposed fat melting wonders (and I don't mean $39.99 for a two week supply) and are the benefits really worth it? Before we get to whether or not they work, let's take a look at what they are and the mechanisms by which they function. Fat burners induce thermogenesis which is the process the body uses to burn fat by altering metabolism. It translates to the production (genesis) of heat (thermo). Therefore, thermogenic aids (fat burners) are aids/agents used in order to facilitate the process of thermogenesis. The active ingredients most prevalent today are ephedrine, caffeine and aspirin (the ECA stack) synergistically functioning together to maximize thermogenesis. Ephedrine, also known as Ma Huang, is an ancient chinese herb and has been around for over five-hundred years. Caffeine, also known as guarana (its herbal counterpart), is said to enhance the effects of ephedrine and to have a supra additive synergistic effect in combination with ephedrine and aspirin. This means that the effects of the ECA stack together are greater than the sum of each of their effects on their own. Aspirin, also listed as white willow bark or salicin complex (salicin is a component of white willow bark and it is this component that led to the discovery of aspirin), has thermogenic properties, as well, and is the final component in this anti-obesity cocktail. Another key ingredient found in some fat burning products is green tea extract. It comes from the latin, Camellia sinesis, and has been used for thousands of years as an immuno-suppressant. The active ingredient has many isoforms but the most active is epigallocatechin gallate (EGCG). There are several other thermogenic ingredients that are found in many of these fat burning supplements including L-tyrosine (precursor for the formation of certain excitatory neurotransmitters, primarily norepinephrine), cordyceps, yohimbe (supposedly possesses the ability to antagonize specific fat receptors which are in great abundance in the hips and butt of women), carnitine (said to enhance the transport of long chain free fatty acids from the cytosol into the mitochondria facilitating fat oxidation), St. John's wort, cayenne pepper and yerba mate. Yikes! But how do they work?! A basic understanding of the nervous system is crucial in order to understand the postulated mechanisms of fat burners. The autonomic nervous system (ANS) is a division of the nervous system that controls autonomic functions like hunger, sleep, respiration, heart rate (HR), blood pressure (BP), etc. This is further subdivided into the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). For the purpose of this article, the SNS is an excitatory system (increased HR, increased BP, vasodilation, etc.) and the PNS is an inhibitory system (decreased HR, decreased BP, vasoconstriction, etc.). There exists a very complex regulatory system requiring special hormones and neurotransmitters within the ANS all working together to maintain homeostasis within the body. Remember, the human body truly is a well-crafted machine. Within the SNS there are also a group of chemicals called catecholamines which are secreted in response to exercise which elicit certain autonomic reactions including increased respiration (you know how you huff and puff after five minutes on the treadmill?), increased HR response (and feel like you wanna die?) and increased BP response (and your capillaries are about to burst?) and these chemicals only bind to special receptors within the body. They include epinephrine and norepinephrine, and as a side note, are also responsible for the anti-depressant quality of exercise facilitating the release of natural opiates. Poppies, poppies... But I digress. What does this all have to do with burning fat? Well, fat burners are sympathomimetic agents. They mimic the actions of the SNS, mainly the actions of the catecholamines. Starting to make sense? If you are working out a lot, cutting back on calories because you're trying to get cut, this results in increased energy expenditure due to a increased catecholamine output and increased SNS activity. The excessive norepinephrine output results in an accelerated thermogenic response. Sympathomimetic agents can counteract this effect by binding to the same receptors that the catecholamines would normally bind to (it's a lock and key situation when dealing with neurotransmitters), thus, bypassing the thermogenic response and allowing the dieting and thermogenesis to occur simultaneously. This is the role of ephedrine in the ECA stack since it is a well-known and effective sympathomimetic amine. Remember when I said there was no free lunch? Well, as the levels of circulating catecholamines increases, so does the production of other thermogenic inhibiting compounds such as adenosine and prostaglandins (hormone-like compounds which are said to promote the production of embolisms in the blood, preventing oxygen-rich blood to circulate to the tissues). This can be counteracted by the addition of methylxanthines (byproducts of caffeine metabolism) and aspirin. Caffeine facilitates the process by antagonizing phospodiesterases (enzymes which break down key components of thermogenesis as well as inhibiting the process of lipolysis (fat metabolism)) and aspirin is said to inhibit prostaglandin synthesis (which is why it is recommended by the American Heart Association as a mechanism for the prevention of cardiovascular disease) therefore allowing norepinephrine to run free and clear to do its thermogenic job. And there you have it. So are they effective? In a study by Daly et al., the thermogenic properties and effectiveness of the ECA stack was observed in twenty-four obese subjects with "difficulty losing weight." In part one of this experiment all subjects were given ECA before meals three times a day for eight weeks. Physical activity was neither encouraged nor recommended and diet was not restricted although nutritional advice was given on calorie restriction and fat content. Some subjects received ECA and some received a placebo. The first four weeks consisted of 75mg ephedrine, 150mg caffeine and 330mg aspirin or the equivalent in placebo. After four weeks the ephedrine dosage was increased to 150mg. Subjects then returned evaluation at weeks one, four, six and eight to have their weight, BP, and HR measured as well as to be interviewed about any reported side effects, compliance and dietary recall. The mean weight loss was 2.2kg +/- .7kg for the ECA group as compared to .7kg +/- .6kg for the placebo group. The significant loss in weight was found to occur after the increase in ephedrine dosage suggesting that there is an optimum dosage for the effectiveness of these fat burners. Reported side effects included jitteriness, dry mouth and loss of appetite. In part two of this experiment eight of the subjects in the placebo group from part one returned five months later and received ECA in an unblinded crossover study. The ephedrine dosage was doubled to 150mg after the first week. The mean weight loss after eight weeks was significantly greater on ECA at 3.5kg versus a mean of 1.3kg lost during the eight weeks on placebo in part one. In part three of this experiment six of the eight subjects in part two continued on ECA for seven to twenty-six months and were monitored on a month to month basis. The average weight loss in five of these subjects was 5.2kg. The sixth subject was left out of the statistics because of a self-induced calorie restriction and exercise program in which she lost 31.7kg (that's 69.7lbs if you don't know the conversion) over the five months. So what does this all mean? Well, it is quite apparent that these fat burning agents are effective. But as you can tell from this particular study, they are much more effective in conjunction with a calorie-restricted diet and exercise program. This is where most people go wrong and then they justify it by convincing themselves that they have a "slow metabolism." They turn to these over-the-counter magic bullets as a substitute for having to get off their lazy you-know-whats and move. Fat burners are on the top of the sports supplement food guide pyramid (has this been approved by the USDA?), not the bottom. Most people looking to get in shape, lose weight and feel better about themselves turn to these products thinking that they are the answer. They aid in the process but they don't necessarily run the show. There is a synergy between diet, exercise and supplementation and if you don't add one to the equation you can't maximize your results. You'll end up wasting your money and there is A LOT of money being wasted in the sports supplement industry today. And then there are the side effects. Besides the jitteriness, dry mouth and decreased appetite, other reported side effects include tachycardia (HR >100bpm), nausea, tremor, teeth grinding, stress, muscle fatigue and my favorite, death. How many cases are there now with fat-burners as the culprit? And isn't there controversy as we speak about placing a ban on it's use? There's controversy for a reason and why risk it. I know from experience that it's possible to achieve a desirable physique without popping pills that wreak havoc on my nervous system. I have a boyfriend for that. So save your money... go buy yourself lunch. References Astrup A, Toubro S, Christensen N and Quadde F. Pharmacology of thermogenic drugs. Am J Clin Nutr. 55:246S-8S, 1992. Dulloo AG, Seydoux J, Girardier L, Chantre P and Vandermander J. Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity. Int J Obes. 24:252-258, 2000. Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P and Vandermander J. Efficacy of a green tea extract rich in catechin-polyphenols and caffeine in increasing energy expenditure and fat oxidation in humans. Am J Clin Nutr. 70:1040-1045, 1999. David Bracco, Jean-Marc Ferrara, Maurice J Arnaud, Eric Jequier and Yves Schutz. Effects of caffeine on energy metabolism, heart rate and methylxanthine metabolism in lean and obese women. Am J Physiol. 269(Endocrinol Metab. 32): E671-678, 1995. Daly PA, Krieger DR, Dulloo AG, Young JB and Landsberg L. Ephedrine, caffeine and aspirin: safety and efficacy for treatment of human obesity. Int J Obes. 17(suppl 1): S73-S78, 1993. Toubro S, Astrup A, Breum L and Quadde F. Safetly and efficacy of long-term treatment with ephedrine, caffeine and an ephedrine/caffeine mixture. Int J Obes. 17(suppl 1): S69-S72, 1993. Landsberg L and Young J. Sympathoadrenal activity and obesity: physiological rationale for the use of adrenergic thermogenic drugs. Int J Obes. 17(suppl 1): S29-S34, 1993. Kristin Reisinger, MS RD, is a New York City-based nutritional consultant, fitness trainer, freelance health + fitness writer and musician. She holds a Master's Degree in Exercise Physiology + Nutrition from Columbia University and is a Registered Dietitian through American Dietetic Association. She is also a competitive figure athlete, former Galaxy competitor, avid snowboarder, rock climber and surfer. She has been competing for over five years and will continue to do so until she is 80. She can be contacted at kristin@kristinreisinger.com.