The Science Behind Fat Burners

We all see tons of products out on the market that say they burn fat—but are they being truthful?  We know that the FDA does not regulate supplements, so how do we truly know if they work or not?  Do we base it off of all the advertising dollars companies put into promoting their products?  I hope you don’t believe them!  Flip through the pages of any fitness magazine and you will see ads for products that “increase strength by over 1000% on the first dose” or “burns 500 times for fat than the leading fat burner”.  Come on, give me a break.  If you believe that nonsense, I’ll sell you some swamp land down in Florida. 

So what really works?  Well, there are studies out there and to be honest, there aren’t a lot of ingredients that help aid in fat burning.  Many are still on the fence and need more studies done to be 100% sure the findings are correct and not bias in any way. 

Let me make this loud and clear…  THIS ARTICLE IS IN NO WAY, SHAPE, OR FORM A REPLACEMENT TO A GOOD SOUND DIET AND EXERCISE PROGRAM!!!  This is not your ticket to sit on the couch and be lazy.  You still need to put in the time in the gym and be patient enough to prepare healthy, whole food meals.

Now let’s dig into what some of the studies show!


Green Tea

Green tea is available in just about any grocery store you will encounter.  If it is already bottled, you can more than likely find it on the shelves where the instant and boxed coffee is along with the other types of tea which you can make yourself.  No matter the form, green tea is accessible just about anywhere you go.  Green tea is also found in many leading fat-burning products on the market.

A study conducted back in 1999 collected subjects and conducted 3 separate trial treatments on them—one of them containing green tea.  What they found was the green tea resulted in a higher 24-hour energy expenditure, which is the amount of energy, measured in calories, that a person uses, (4%; P < 0.01) and a significant decrease in 24-hour respiratory quotient which is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed per unit of time by the body under steady-state conditions, (from 0.88 to 0.85; P < 0.001).  By indicating a higher expenditure, they concluded in their findings that green tea does indeed have thermogenic properties and promotes fat oxidation. 



Caffeine as we know is found in many sodas as well as tea and coffee and is a stimulant.  Not only can it be found in these liquids but you can also find it in a pill form as well.  Depending on the source, caffeine can range from a mere 20mg (or less) all the way up to 200mg (sometimes more if an energy drink).  Caffeine is found in almost every fat-burning supplement on the market that is not deemed “stimulant-free”.

There were four trials of studies done.  The first trial completed was using normal weight subjects with only 8mg of caffeine versus a placebo.  The results of this trial showed the metabolic rate increased dramatically after only a 3-hour period.  This first trial also showed “plasma free fatty acid levels rose from 432 +/- 31 to 848 +/- 135 muEq/liter and were accompanied by significant increases in fat oxidation during the last hour of the test”.  The second and third trials were using the control and obese subjects and only 4mg of caffeine.  Both groups showed an increase in metabolic rate but only the control group in these trials showed an increase in fat oxidation.  In the fourth trial coffee was drank with a meal in which again, showed a thermic effect and increased fat oxidation.  So overall, caffeine can be used to increase metabolic rate no matter if the subject is of normal body weight or obese.  However, the limiting factor is that only the normal weight group showed greater fat oxidation.



Conjugated linoleic acid (CLA) to many people’s surprise is actually a free fatty acid found in many meats and dairy products.  Therefore, not only can you get this in many of the foods you eat, but also in a supplement form.  The supplement form is the easiest to take as you would need to eat a lot of the foods mentioned to get the amount needed to truly show results.

A study containing both overweight and obese subjects was conducted where the subjects were split into five groups where one group go a placebo and the other four got different dosages of CLA for 12 weeks.  At the end of the study, all groups who were given the CLA had a greater reduction in body fat mass (P = 0.03).  The groups receiving 3.4 and 6.8g of the CLA showed the greatest reduction in body fat compared to the other groups (P = 0.05 and P = 0.02). 



Hydroxycitric acid (HCA) is found in several fat-burning supplements on the market today.  What most people don’t realize is that HCA is actually a compound found in garcinia cambogia (which is a type of fruit).  Although it doesn’t necessarily burn fat by any direct method, this is an ingredient in several fat-burning products on the market due to its appetite suppression properties. 

A study containing mildly overweight females was done over a period of 12 weeks.  One group took a placebo while the other group took in 1.2g of HCA each day (total but separated into smaller dosages) around 30-60 minutes prior to meals.  Both groups did lose weight, however the group taking the HCA lost significantly more weight (3.7±3.1 kg versus 2.4±2.9 kg).


Whey Protein

Whey protein really has not fat burning properties—however I added it to this article because it plays a very important part in preserving muscle mass while on a restricted caloric intake which aids in fat loss. 

There was a study done in 2008 where subjects (age range between 25-50 and with no major health issues) were part of a 12-week study with a caloric intake restricted 500 calories each day.  One group took a protein shake twice a day while the other had a placebo.  At the end of 12 weeks both groups had lost weight.  Although the difference wasn’t huge, it still showed the protein group lost more than the controlled group (3.63 vs. 2.11 kg, P = 0.01).  It was also shown that the subjects taking the whey protein also lost less lean muscle than the controlled group (1.07 vs. 2.41 kg, P = 0.02).  The final results came to show the total ratio of fat loss versus muscle loss was greater in the group taking the protein shake (3.39 vs. 0.88).



Acheson KJ, Zahorska-Markiewicz B, Pittet P, Anantharaman K, Jequier E. “Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals.”  The American Journal of Clinical Nutrition.  Web.  21 June 2010.

Blankson H, Stakkestad JA, Fagertun H, Thom E, Wadstein J, Gudmundsen O.  “Conjugated Linoleic Acid Reduces Body Fat Mass in Overweight and Obese Humans.”  The Journal of Nutrition.  2000.  Web.  21 June 2010.

Dulloo A, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.  “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.”  The American Journal of Clinical Nutrition.  December 1999.  Web.  21 June 2010.

Frestedt J, Zenk J, Kuskowski M, Ward L, Bastian E. “A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: a randomized human clinical study.” Nutrition & Metabolism.  1 May 2008.  Web.  21 June 2010.

Mattes R, Bormann L.  “Effects of hydroxycitric acid on appetitive variables.”  Physiology & Behavior.  October 2000.  Web.  21 June 2010.

Author:  Matt Weik

Follow Matt on Twitter @weikfitness

If you are interested in online training please email Matt at