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Facts About Fat Burners

Reading Time: 5 minutes 61 seconds

BY: Dustin Parsons

DATE: 2019-09-20

There are hundreds, perhaps thousands of nutritional products and schemes on the market promising the uninformed consumer faster and easier fat loss. The truth is, the vast majority of these products burn nothing but your money. The few products that actually aid in fat burning or weight reduction can be quite dangerous, even deadly! Nonetheless, most people do not take the time to research the efficacy and safety of a product before they jump on the quick-fix bandwagon. As a fitness trainer, keep your scope of practice in mind and remember that ignorance is not a valid excuse for recommending ineffective or unsafe fat loss products or schemes. Let's take a look at the safety and effectiveness of some commonly used fat loss ergogenic aids. L- carnitine, caffeine, ephedrine, and low carb/high protein diets will be reviewed in this article.


Carnitine plays a key role in the mobilization of body fat for fuel in the body. It is for this reason that it has become popular as a dietary supplement. The theory is, the more carnitine you can ingest, the more fat your body will burn. Athletes like it because a greater dependency on fat for fuel would spare precious carbohydrates, increasing aerobic endurance. Several recent controlled studies have demonstrated, in both athletes and moderately trained individuals, that carnitine supplementation has no effect on fat or carbohydrate metabolism either at rest or during exercise in healthy individuals. (1) Despite the use of L-carnitine in thousands of weight loss products, it does not aid fat burning or weight loss in any way.

Ma-Huang and Ephedrine

The drug Ephedrine, which is the main constituent of the herb Ma-huang, is a major ingredient in many weight loss nutritional supplements on the market today. Ephedrine speeds up the metabolism by stimulating the release of adrenaline in the body. Adrenaline stimulates the release of glucose from the liver and free fatty acids from the body's fat stores, increasing the availability and use of both glucose and fat for ATP production. (6) Unfortunately, adrenaline can also have very negative effects on the body.

Several studies have shown that ephedrine, when combined with caffeine, can aid in overall weight loss in obese people due to its adrenal effects. (2,5) These conclusions are somewhat limited because all subjects used were obese, and measurements of body composition were not used at any time. Only overall body weight and body mass index (BMI) were used as measures. What does this conclusion mean for those that are not currently considered obese? The answer is not known. It is likely that an ephedrine/caffeine combination (all research has shown that ephedrine must be taken with caffeine to have any weight loss effect) will result in overall weight loss, but more research is needed to determine if lean body mass is spared with its use.

More research is NOT needed to verify that ephedrine use has horrible, often deadly, side effects. The FDA has received over 1400 reports of adverse side effects associated with ephedrine use. Medical problems have ranged from high blood pressure, irregular heart rate, insomnia, nervousness, tremors and headaches, to seizures, heart attacks, strokes and death. (4)

It is highly recommended that ephedrine-containing products be avoided because of possible side effects and questionable results. If you choose to take ephedrine, side effects can be minimized by first seeking recommendations from a physician.


Caffeine is a drug that is frequently used all over the world, usually for its stimulant effects. Caffeine increases alertness, lowers the perceived exertion of exercise and decreases reaction time. Caffeine has another effect on the body that few people know about. It also acts as a fat burner!

Caffeine works by increasing the rate of fatty acid metabolism, and decreasing the rate of carbohydrate (glucose) metabolism during aerobic exercise. Every study done on the effects of caffeine during aerobic exercise that has measured muscle glycogen levels, has found that glycogen is spared after ingestion of only 150 to 250 mg of caffeine. An increased reliance on fat, and decreased reliance on glucose and glycogen translates into increased aerobic exercise endurance and increased time to exhaustion. In addition to this, for a given amount of calories used during exercise, more calories will come from body fat if caffeine is consumed prior to exercise.

Caffeine does have side effects as well. At high doses (more than 15 mg/kg body weight), caffeine can produce slowed heart rate, hypertension, nervousness, irritability, insomnia, and gastrointestinal distress. (7) In addition to this, it is a diuretic that blocks the release of antidiuretic hormone. This causes the kidneys to excrete more fluid than normal, which can dehydrate the body. (9)

Caffeine is one of the least marketed, but most effective "fat burners" available. It accomplishes what L-carnitine claims to do, but does not do. Caffeine will not help you lose weight on its own, but when taken before aerobic exercise, can increase fat burning and help you exercise longer by delaying the onset of fatigue. Caffeine will not have any beneficial effect on anaerobic exercise. If you use caffeine, please use it sparingly and in small doses. Be aware of the side effects listed above, and see a physician if you suspect any complications.

High Protein/ Low Carbohydrate (Ketogenic) Diets

In recent years, many diet marketers are focusing on high protein (more than 35% of calories), restricted carbohydrate diets as a means of forcing the body to burn more fat. The approaches vary with the marketer, but basically they say that if your body does not have carbohydrates available for fuel, more fat will be burned, and thus more body fat will be lost.

The truth is, there is no scientific evidence to support that this theory will translate into improved body composition or fat loss. It is true that a large volume of weight will be lost as glycogen (stored carbohydrate) depletes in the muscle and liver, but this weight is from water, not fat loss. This will not help body composition or overall health. It is also true that the body will rely more on free fatty acids for fuel when muscle glycogen is depleted, but the body will rely much more on amino acids (protein) supplied from the breakdown of lean tissue as well. (3) So while you may burn more fat, you will also burn more muscle. In addition to this, individuals on a carbohydrate-restricted diet have lower energy levels and experience shorter time to fatigue during exercise. (9) This means that workouts will likely be cut short and lower in intensity.

Almost all sport scientists agree that those engaged in regular exercise need more protein than the RDA. Most recent research shows that individuals engaged in heavy strength training need 1.5 to 2.25 times the RDA at .6 to .8 grams of protein per pound of body weight per day, with endurance athletes just slightly less. (9) Still, this amount is far less than the 35 to 40% of daily calories advocated by the ketogenic diets. There is no evidence that this gross consumption of protein, with or without a heavy restriction of carbohydrates, will do anything beneficial for the body.

Additional protein is just as likely to end up as stored body fat as is excess carbohydrates. The fears that "carbs will make you fat" are basically a result of heavy marketing by ketogenic diet manufacturers. Carbs are still, and always will be the body's preferred source of calories. The body, and exercise capacity in general, suffers without adequate carbohydrates. Carbohydrates, especially from complex sources, are extremely unlikely to end up as stored bodyfat even when eaten in excess, provided the individual is eating adequate protein and not consuming excessive total calories. (8)

Ready to learn more about nutrition and how it can help clients achieve healthy results? Check out the ISSA's nutrition course today!

  1. Armsey et al. (1997). Nutritional supplements: science vs hype. The Physician and Sportsmedicine. 25,6.

  2. Astrup et al. (1992). The effect and safety of an ephedrine/caffeine compound compared to ephedrine, caffeine and placebo in obese subjects on an energy restricted diet. Int J Obes relat Metab Disord. 16(4), 269-277.

  3. Clark, N. (1996). The power of protein. The Physician and Sportsmedicine. 24,4.

  4. Crabtree, J. Ma huang, the chinese herb used for weight loss- any danger? Health-Doc.com/healthysolutions/MaHuang.html.

  5. Daly et al. (1993). Ephedrine, caffeine and aspirin: safety and efficacy for treatment of human obesity.Int J Obes relat Metab Disord. 17, 73-78.

  6. Fox, S.I. (1996). Human Physiology, 5th ed. Wm. C. Brown Publishers.

  7. Hawley, J.A. (1998). Fat burning during exercise: can ergogenics change the balance? The Physician and Sportsmedicine. 26,9.

  8. Jequier, E. (1994). Carbohydrates as a source of energy. American Journal of Clinical Nutrition, 59, 682-685.

  9. Wilmore J.H., Costill, D.L. (1999) Physiology of sport and exercise, 2nd ed. Champaign Il, Human Kinetics

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