You’re likely familiar with the popularity of the stimulant drug caffeine given most people habitually use it in some capacity. Caffeine has been used for decades as an ergogenic aid/performance-enhancing supplement due to its ability to “excite” the central nervous system. Naturally, the use of caffeine specifically for fat loss is a popular area of research in the health/fitness industry.
Does caffeine really hold potential to enhance your fat burning efforts, and if so, when should one take it to maximize their fat loss? Moreover, what is the proper dosage to take in and what are the pros/cons to continual use of caffeine. These are all questions to be examined in this article, so without further ado let’s move onto the next sections.
What is caffeine?
It’s pertinent to briefly cover the chemical nature of caffeine and what it actually is. The chemical nomenclature for caffeine is “1,3,7-trimethylxanthine” (don’t worry if you’re not a chem whiz, I’ll try and keep this in layman’s terms). Methylxanthines are alkaline, organic (i.e. carbon-based) substances that stimulate the CNS and heart, and they are naturally abundant in tea leaves, coffee beans, some fruits and other foods/plants.
Physiologically speaking, the ingestion of methylxanthines postpone the breakdown of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) via inhibition of phosphodiesterase (PDE) enzymes; thus caffeine is considered a PDE inhibitor. Since cAMP and cGMP are crucial messengers in cell signal transduction, the metabolic processes in the cell are sent into “overdrive” after the ingestion of PDE inhibitors.
Does caffeine help fat loss efforts, and if so, how?
There is some speculation that caffeine may enhance fatty acid oxidation through increases in catecholamines (such as adrenaline). While research on caffeine’s ergogenic effects in athletic performance is abundant, there remains to be conclusive evidence that caffeine ingestion significantly alters substrate metabolism in muscles during exercise. That being said, there are other possible mechanisms for caffeine to enhance fat loss, so we can’t write it off as useless just yet.
One of the proposed mechanisms for caffeine enhancing fat loss is through an increase in 24-hour energy expenditure (via increased metabolic rate). Moreover, the thermic effect of meals ingested with caffeine are more pronounced than meals ingested without caffeine. 
Despite the relatively short half-life of caffeine, the duration of its effects may last for several hours after ingestion. It appears that caffeine, when coingested with carbohydrates, does enhance carbohydrate oxidation during endurance training, but this likely mediated through enhanced intestinal absorption as opposed to increased catecholamine levels.
The most compelling evidence, in my opinion, for caffeine use enhancing fat loss is actually through its effects on exercise performance. What I would argue, based on the research, is that since caffeine has been shown to augment both aerobic and anaerobic exercise, as well as lower the rate of perceived exertion (RPE), that the “extra” fat loss achieved is a secondary effect due to the increased exercise output.[5,6] Essentially, after taking caffeine, you generally have an increased athletic performance capacity, thus you can work harder and longer than those who workout without caffeine use beforehand; this in turn would likely increase caloric burn from exercise.
When should caffeine be taken for fat loss and at what dosage?
Most studies examining caffeine’s effect on athletic performance are carried out roughly 1-2 hours after ingestion caffeine. It’s impossible to give all-inclusive dose timings for trainees since different individuals may metabolize caffeine at different rates. Furthermore, caffeine absorption may be slowed with concomitant ingestion of nutrients.
As a starting point (and to assess your tolerance), try taking caffeine on an empty stomach about an hour before training. If you prefer to take caffeine with a meal, give yourself a bit more time before hitting the gym. If you find your performance in the gym is indeed bolstered after caffeine ingestion, than there is little reason to alter your approach. On the contrary, if you notice no change or a decrease in performance, you will either want to adjust your dose and/or manipulate the dose timing.
Dosage wise, it is generally recommended to take 1-3mg per kg of bodyweight (remember: 2.2lb=1kg). If you’re a 180lb (~81kg) athlete, your dose range will land around 80 to 240mg. Do not go too crazy with caffeine dosing since there isn’t much extra benefit to superfluous amounts and it can in fact be lethal/toxic at high enough doses (>5g). Be safe and methodical with caffeine; it is a drug, so treat it as such.
1. Graham, T. E., Battram, D. S., Dela, F., El-Sohemy, A., & Thong, F. S. (2008). Does caffeine alter muscle carbohydrate and fat metabolism during exercise?.Applied Physiology, Nutrition, and Metabolism, 33(6), 1311-1318.
2. Kobayashi-Hattori, K., Mogi, A., Matsumoto, Y., & Takita, T. (2005). Effect of caffeine on the body fat and lipid metabolism of rats fed on a high-fat diet.Bioscience, biotechnology, and biochemistry, 69(11), 2219-2223.
3. Acheson, K. J., Zahorska-Markiewicz, B., Pittet, P. H., Anantharaman, K., & Jequier, E. (1980). Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals. The American journal of clinical nutrition, 33(5), 989-997.
4. Yeo, S. E., Jentjens, R. L., Wallis, G. A., & Jeukendrup, A. E. (2005). Caffeine increases exogenous carbohydrate oxidation during exercise. Journal of Applied Physiology, 99(3), 844-850.
5. Doherty, M., & Smith, P. M. (2005). Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta‐analysis. Scandinavian journal of medicine & science in sports, 15(2), 69-78.
6. Doherty, M., Smith, P. M., Hughes, M. G., & Davison, R. R. (2004). Caffeine lowers perceptual response and increases power output during high-intensity cycling. Journal of sports sciences, 22(7), 637-643.
7. Del Coso J, Salinero JJ, González-Millán C, Abián-Vicén J, Pérez-González B. Dose response effects of a caffeine-containing energy drink on muscle performance: a repeated measures design. J Int Soc Sports Nutr. 2012 May 8;9(1):21. PubMed PMID: 22569090.