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Fat Burning Update

by Colin Carriker, MS and Len Kravitz, PhD on Mar 16, 2012


What science says on the latest claims about weight loss supplements.

The concept of fat loss can become an obsession for many people, whether they are exercise enthusiasts, elite athletes or occasional gym visitors. Every day, personal trainers hear questions like “What exercises burn the most calories?” and “Which nutritional supplements enhance fat burning?” From a health perspective it is important to emphasize to clients that the more abdominal fat (that is, visceral or central fat) they have, the greater their risk for developing insulin resistance, type 2 diabetes, heart disease, some cancers (endometrial, breast and colon) and some disabling degenerative diseases of the joints (WHO 2011). This column will answer 10 contemporary questions on fat burning and fat-burning supplements. See Figure 1 for an illustration of the main claims made about various fat-burner supplements.

1. Will I prevent weight gain by predominantly consuming a diet of carbohydrates and proteins?

Probably not. Fat contains 9 calories per gram; carbohydrate, 4 calories per gram; protein, 4 calories per gram; and alcohol, 7 calories per gram. Ultimately, overconsumption of total calories coupled with reduced caloric expenditure (via reduced physical activity) results in a caloric imbalance that produces a net caloric gain in weight—often as increased body fat. If fat is meaningfully reduced in the diet, there are still other substrate avenues through which extra calories can enter the body.

Bray et al. (2012) investigated overconsumption of calories in diets with low, normal and high amounts of protein. Interestingly, the increases in body fat were similar in all three protein diet groups. The authors concluded that increased calorie consumption alone was responsible for the similar increases in fat content across the three groups. Thus, it may be inferred that a positive energy intake above bodily needs from carbohydrate sources will also result in an increase in body fat.

2. Does L-carnitine supplementation increase muscle mass, improve fat metabolism and enhance fat loss, as the advertising claims?

We do not know for sure. L-carnitine exists in large quantities in meat and has been a supplement of interest for two decades. The primary function of L-carnitine is to transport long-chain fatty acids across the inner membrane of a muscle cell’s mitochondrion (ATP synthesis organelle), where the fatty acids are further broken down.

Some believe that regular L-carnitine supplementation will help with weight loss by increasing the cell’s concentration of carnitine, thus increasing fatty acid transport for enhanced fat metabolism. Unfortunately, there is no solid scientific evidence supporting this claim (Jeukendrup & Randell 2011).

3. Is consumption of liquid calories a viable weight loss plan?

No. While it may seem logical to think that liquid calories won’t add body fat, this couldn’t be further from the truth. What should be recognized is the energy balance (calories in versus calories out) over a day or a week.

Many beverages are sweetened with sugar and have very little nutritional benefit. Research indicates that high consumption of beverages with added sugars—particularly drinks sweetened with high-fructose corn syrup—may be contributing to the current obesity epidemic (Bray, Nielsen & Popkin 2004).

4. Will the intake of caffeine improve energy expenditure at rest and during exercise?

Yes, but not by much. Caffeine has been shown to increase sympathetic nervous system activity, thus releasing fatty acids from adipose and intramuscular tissues’ storage depots.

Caffeine has also been associated with metabolic processes that enhance fat breakdown (Jeukendrup & Randell 2011). Although the effects of caffeine do seem to acutely enhance metabolism at rest and during low-intensity exercise (less so during moderate- to high-intensity exercise), Jeukendrup and Randell conclude that the effects are small.

5. Should all fat intake be reduced in the diet?

No. Some fats, including both saturated and trans fatty acids, should be consumed minimally. However, research suggests a link between omega-3 fatty acids in the diet and a reduced incidence of cardiovascular disease.

There is also evidence of a link between omega-3 fatty acids and the management of hypertension (depending on the degree of an individual’s hypertension). And omega-3s may aid in lowering triglycerides and reducing the risk of mortality from cardiac arrhythmias (Kris-Etherton, Harris & Appel 2002).

6. Does fucoxanthin supplementation lead to weight loss?

Possibly. Fucoxanthin is a carotenoid found in edible brown seaweed. Some weight loss companies promote it as a weight loss supplement.

The one study on this product showed positive results, though caution is suggested because one of the authors works for the company that holds patents for fucoxanthin (Jeukendrup & Randell 2011). Also, seaweed has several times more iodine than most adults require on a daily basis. Therefore, a possible side effect could be changes in thyroid function due to a surplus of iodine.

7. Will conjugated linoleic acid boost fat loss?

Possibly. Conjugated linoleic acid (CLA) is promoted as an anti-obesity agent. Claims suggest it increases energy expenditure, fat oxidation and lipolysis (the disassembly of fats) and dampens appetite. More recent research shows that supplementation of 3 grams of CLA per day will result in very modest fat loss (Jeukendrup & Randell 2011).

8. What are the best exercises for weight loss?

It depends. First and foremost, you have to determine which exercises clients consistently enjoy doing. A combination of resistance exercise and cardiovascular training is key to weight loss success.

Resistance training helps preserve muscle mass during calorie-restricted eating. Also, energy expenditure increases modestly after each training session for a couple of hours. To increase energy expenditure from exercise without causing overuse injuries, a combination of weight–bearing and non-weight–bearing cardiovascular exercises is recommended (i.e., jogging, cycling, elliptical training, rowing, stair stepping, etc.).

The best approach is to mix up cardiovascular workouts to include long, low-intensity continuous training bouts; short, fast continuous-exercise training sessions; and high-intensity interval training.

9. Will taurine promote weight loss?

Possibly. Popularly promoted for weight loss, taurine is an amino acid that is necessary for normal skeletal muscle functioning. One study has linked taurine ingestion with a favorable increase in fat oxidation during exercise (Jeukendrup & Randell 2011). Further investigations are necessary to fully determine the efficacy of taurine for weight management programs.

10. Is forskolin a weight loss supplement of the future?

Possibly. Forskolin is produced by the roots of a family of coleus plants cultivated in India, Thailand and parts of Southeast Asia. It is hypothesized that forskolin may increase activation of hormone-sensitive lipase, an enzyme that increases the breakdown of fat and thus improves fat oxidation.

Although there is only one published study on forskolin, the positive results suggest more study is warranted to determine optimal dosages for this supplement’s use for fat metabolism.


Bray, G.A., et al. 2012. Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating. The Journal of the American Medical Association, 307 (1), 47–55.

Bray, G.A., Nielsen S.J., & Popkin, B.M. 2004. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. American Journal of Clinical Nutrition, 79 (4), 537–43.

Jeukendrup, A. E., & Randell, R. 2011. Fat burners: Nutrition supplements that increase fat metabolism. Obesity Reviews, 12, 841–51.

Kris-Etherton, P.M., Harris, W.S., & Appel, L.J. 2002. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation, 106, 2747–57.

LaMonte, M.J., & Blair, S.N. 2006. Physical activity, cardiorespiratory fitness, and adiposity: Contributions to disease risk. Current Opinion in Clinical Nutrition & Metabolic Care, 9 (5), 540–46.

WHO (World Health Organization). 2011. Overweight and obesity.; retrieved Jan. 24, 2012.

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About the Authors

Colin  Carriker, MS

Colin Carriker, MS IDEA Author/Presenter

Len Kravitz, PhD

Len Kravitz, PhD IDEA Author/Presenter

Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico in Albuquerque, where he recently won the Outstanding Teacher of the Year award. Len w...