Does Caffeine Increase Fat Metabolism?

Caffeine’s ergogenic effects have been studied for decades, with multiple research journals confirming its enhancements to exercise, reduction in fatigue, and increased muscle glycogen synthesis. Caffeine works by blocking the inhibitory neurotransmitter adenosine. But what about caffeine’s role in fat metabolism? Can this substance aid our bodies in using fat as a primary substrate during workouts and even rest?

We have covered caffeine extensively, as it’s one of the most consumed ergogenic aids by athletes and general populations alike. From uncovering common myths about coffee to understanding its post-workout effects, we’ve taken a deep dive into the world of caffeine. So grab your cup of coffee, and let’s look into caffeine’s effect on fat metabolism!

Fat Metabolism | The Science

To understand caffeine’s effect on fat metabolism, we first need to look at how fat plays various roles in our body’s metabolic pathways. There are entire degrees dedicated to studying human metabolism- so we are going to barely touch the surface here. During exercise (and rest,) our bodies utilize carbohydrates, fats, and amino acids to fuel our bodies. During lower-intensity work, such as a Zone 2 cycling workout, our bodies prefer fat as a primary substrate. Through metabolic processes, such as gluconeogenesis, substrates like fat and amino acids get converted into Glucose. At roughly 60% VO2 max, our bodies oxidize the most amount of fat.

Chart: fat Oxidation compared to workout intensity

Source: ResearchGate

Caffeine’s Role

A recent review by the International Journal of Sport Nutrition and Exercise Metabolism found that caffeine consumption among athletes reports a highly significant but small effect size (ES = 0.39) of caffeine to increase fat metabolism. While the variability is small, there is a proven metabolic advantage in terms of fat oxidation. The review also denotes that fat metabolism at rest and exercise remains elevated with the consumption of caffeine. This journal reviewed 94 studies and found that gas exchange measurements were far more accurate at measuring fat oxidation than normal blood draws. “The ES (effect size) was lower when studies utilized methods based upon whole-body gas exchange analysis compared with lipolytic blood parameters (e.g., glycerol, FFA).”

Caffeine & Metabolism

Due to its effect on thermogenesis, caffeine can increase your resting metabolic rate (RMR) by 3-11%. Therefore, its effects during both rest and work can be advantageous. Issues begin to arise when we talk about tolerance. Those that consume caffeine regularly may experience less effective resting metabolic rates than those who are sensitive to caffeine.

Conclusion

So does drinking coffee make you skinny?

There is varied evidence that caffeine causes a noticeable increase in fat metabolism. This specific review noted a small yet significant change. More research, including a randomized control trial, would greatly benefit the understanding of caffeine’s role in fat metabolism- both at work and at rest.

What’s equally notable in this review is the fact that fat metabolism and carbohydrate metabolism may have skewed some of the results during gas-exchange testing. This limitation further aids the need for additional research and controlled trials on this topic.

In any case, caffeine has shown time and time again that it is an effective ergogenic aid. Although data is nominal for its role in fat metabolism, caffeine can reduce perceived effort, increase glycogen restoration post-workout, and stimulate your central nervous system during intense workouts. I am excited to see more studies come out on this topic, and will post a follow-up article if/when that happens! For now, keep drinking that coffee!

---

Bibliography

Kerksick CM, Arent S, Schoenfeld BJ, et al. International society of sports nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition. 2017;14(1). doi:https://doi.org/10.1186/s12970-017-0189-4

Conger SA, Tuthill LM, Millard-Stafford ML. Does Caffeine Increase Fat Metabolism? A Systematic Review and Meta-Analysis. International Journal of Sport Nutrition and Exercise Metabolism. 2022;33(2):1-9. doi:https://doi.org/10.1123/ijsnem.2022-0131

LeBlanc J, Jobin M, Côté J, Samson P, Labrie A. Enhanced metabolic response to caffeine in exercise-trained human subjects. Journal of applied physiology (Bethesda, Md : 1985). 1985;59(3):832-837. doi:https://doi.org/10.1152/jappl.1985.59.3.832

Glaister M, Gissane C. Caffeine and Physiological Responses to Submaximal Exercise: A Meta-Analysis. International Journal of Sports Physiology and Performance. 2018;13(4):402-411. doi:https://doi.org/10.1123/ijspp.2017-0312