Weight Loss Supplements: Are Fat Burners Really Worth It?

Commercial weight loss supplements are often filled with caffeine and one or more of the following natural extracts reported to have “fat burning” effects: green tea extract, green coffee bean, raspberry ketone, and garcinia cambogia. This article will describe what these compounds are all about, their effectiveness and safety.


Several weight loss supplements are marketed as being “fat burners”. The “fat burn” refers to (in a more scientific term): a specific biochemical process called fat oxidation, where body fat (“lipids”) are broken down (“lipolysis”) and used by the body as an energy source, or alternatively released as heat2. Today’s weight loss supplements promise to enhance this process, to cut the fat and pounds, upon ingestion of the following compounds:

  1. Green Tea Extract. Rich in catechins, green tea extract is reported to enhance fat oxidation by increasing the availability of noradrenaline within the blood3. Noradrenaline is a hormone with many roles, which includes stimulating fat oxidation for energy purposes. This is the same chemical our bodies release during the “fight-or-flight” response when we are placed in a seemingly harmful or stressful situation. Some studies have also suggested that catechins reduce the absorption of fat from our diet.


  1. Green Coffee Bean. A biologically active component found within green coffee beans is chlorogenic acid (CGA). CGA stimulates fat oxidation in a similar fashion as catechins Additionally, a recent study suggests that CGA may have anti-diabetic properties as it was shown to regulate blood sugar levels4. Unfortunately, coffee drinkers may not receive these benefits, as the roasting of green coffee beans produces another compound called HAQ, which supposedly reduces the beneficial effects of CGA.


  1. Raspberry Ketone. A compound found within red raspberries, used in several processed foods and cosmetic products to add flavoring and aroma. The use of raspberry ketone in weight loss gained popularity in 2012 when it was showcased on the Dr. Oz show. Just like green tea and green coffee bean extracts, raspberry ketone also increases noradrenaline levels.


  1. Garcinia Cambogia. This is a type of small tamarind fruit that hails from Southeast Asia. Garcinia cambogia is stipulated to reduce the accumulation of body fat via the inhibition of citric acid lyase, which is an enzyme involved in the synthesis of fat. This effect is due to the high content of hydroxycitric acid (HCA) that is found within the fruit. Some studies also report that HCA causes weight loss by increasing the release of serotonin, a hormone known to boost one’s mood and reduce appetite5.


The research shows large variability in the effectiveness of these compounds to actually increase fat oxidation rates and reduce fat mass. While some studies show significant reductions in weight (up to 5% of total body weight) over a 3 month period, other studies show absolutely no effect. The variability arises due to differences in supplements used during the clinical studies, as well as the types of individuals tested (i.e. we all respond differently due to our genetics, composition and lifestyle). Thus, while one product may be useful for one person in improving body composition, in another person there will be no significant changes.

The most worrisome fact about these weight loss supplements is the effects they have on other parts of the body. As mentioned above, most of the “fat burning” components act to increase noradrenaline levels. Noradrenaline not only has effects on fat tissues within our bodies, but also on our lungs, brain, muscles, heart, etc. While these effects are useful during the “fight-or-flight” response (or similarly during exercise) to allow us to escape quickly (or workout harder and faster), chronically heightened levels of noradrenaline is extremely harmful. Consequently, studies done on both animals and humans have reported side effects that include dry mouth, headaches, insomnia, vomiting, abdominal pain, tremors, adverse cardiovascular events (e.g. high blood pressure, abnormal heart rhythms), kidney failure, psychological disorders, and seizures.


Before you consider using a weight loss supplement, even one as harmless sounding as “garcinia cambogia”,  think about how you’ll feel if the product does not work for you, the money you may have wasted or the potential side effects. Best bet is to discuss with your doctor first, and consult with a health and fitness coach on healthier, more natural ways to lose the fat and excess pounds. Always be critical before trying a new health supplement, and understand that the promises that the companies selling these products make often do not match up with the findings from unbiased research studies.



1 Marks (2004). Obesity in America: It’s getting worse. Clinical Diabetes 22(1):1-2

2 Thermogenesis. American Journal of Clinical Nutrition 23(8):1009-1010 Retrieved from: ajcn.nutrition.org/content/23/8/1009.full.pdf

3 Westerp-Plantenga et al. (2006). Metabolic effects of spices, teas, and caffeine. Physiology and behavior 89(1):85-91

4Ong Wei et al. (2013). Anti-diabetic and anti-lipidemic effects of chlorogenic acid are mediated by AMPK activation. Biochemical Pharmacology 85: 1341-1351

5Onakpoya et al. (2011). The use of garcinia extract (hydroxycitric acid) as a weight loss supplement: a systematic review and meta-analysis of randomized clinical trials. Journal of Obesity 2011, article ID 509038



Amanda is a recent Master’s graduate from the University of Ottawa, where she completed exercise physiology-related research within the department of Cellular and Molecular Medicine. In her free time, you can find her out running the Rideau canal in Ottawa or at the gym for her favorite group exercise classes.