Caffeine is everywhere - coffee, tea, energy drinks, and even some medications. It is so widespread and affordable compared to other supplements that it’s no wonder it’s a popular go-to performance enhancer for athletes. The question remains - how effective of a performance enhancer is caffeine really, how much would I have to drink, and can it help me lose weight?

The Effects of Caffeine on Your Body

Caffeine works to combat tiredness by attaching to adenosine receptors in the brain. Adenosine is famously known as the “fight or flight” hormone, but it also plays a key role in the sleep wake cycle. When adenosine molecules attach to adenosine receptors in the brain, it causes sleepiness and sends the message that it is time to rest. The molecule caffeine is shaped very similarly to adenosine and has the ability to bind to adenosine receptors, effectively blocking adenosine molecules from binding. When this happens, the release of neurotransmitters like dopamine and norepinephrine increases, making you feel more energized and awake. In other words, caffeine does not decrease a person’s need for sleep, it only masks the symptoms of sleepiness.

Exercise Performance Improvements

Caffeine is a very well documented exercise performance enhancer. The average increase in performance recorded is 12%, particularly in endurance activity. It seems that sprinters see very little benefit from caffeine in their performance, whereas long distance runners see a much greater benefit. This could in part be due to the fact that the stimulatory effects of caffeine peak around 30 to 75 minutes after ingestion. It’s pretty difficult to gauge the ideal timing of caffeine ingestion when your sport is 60 seconds long versus 60 minutes long. For this reason, it generally isn’t recommended to use caffeine as a performance enhancer for cardiovascular activity lasting 20 minutes or less. There also isn’t a great argument for caffeine before strength training either. Caffeine may help resist fatigue, but it hasn’t proven to help increase maximal strength exertion.

Ideal Dose

The research overall seems to come to the conclusion that a dose of caffeine between 1.5-4 mg per pound of body weight is enough to show performance enhancements. That’s equivalent to about one or two 16 oz coffees for most people. It’s important to note that more is not necessarily better; coffee in particular is notorious for causing nausea at extremely high doses, and those adverse side effects could completely diminish any performance benefit you’re hoping for. Additionally, a dose of 1.5-4 mg/lbs may be ineffective in heavy coffee or soda drinkers. Someone with a high tolerance is much less likely to see a performance benefit.

Caffeine and Metabolism

Caffeine is not only sold as an exercise performance enhancer, but also as a metabolism increasing and fat burning supplement. So does caffeine really increase metabolism and help with weight loss? Sort of. Some studies show evidence of caffeine increasing the resting metabolic rate, or number of calories burned at rest, in study participants by between 3-11%. That sure sounds promising, however, that data comes with two major caveats. One problem is that the increase in RMR observed was about twice as great in healthy weight individuals than in obese individuals. The other problem is that these effects are incredibly short term, because people develop a tolerance to caffeine pretty quickly. Bottom line, going overboard with your caffeine intake probably isn’t going to help you lose weight.

Caffeine and Hydration

You may be concerned with drinking coffee as your caffeine source before exercise due its diuretic effect, however, there is no need to be concerned. The “coffee is dehydrating” myth came from early research observing the increase in urination shortly after drinking coffee. It wasn’t until later when we compared the increase in urination shortly after drinking coffee to the increase after drinking water that we realized coffee isn’t in fact dehydrating. Coffee is included in overall fluid ingestion, just as water is.

Caffeine Content of Common Foods and Beverages

Coffee (8 oz) - 65–135mg

Espresso (2 oz) - 100mg

Tea (8 oz) - 50mg

Soda (12 oz) - 35–45mg

Red Bull (8.3 oz) - 80mg

Rockstar (16 oz) - 160–280mg

Gels - 20–25mg

Chocolate (1.5 oz) - 10–30mg

Caffeine tablets - 200mg

Mountain Dew (12 oz) - 55mg

Take Aways

Caffeine is not likely to enhance exercise performance for activity lasting 20 minutes or less.
Caffeine can increase metabolism, but not enough to make a significant dent in weight loss.
Tolerance to caffeine builds quickly and may mute initial performance and metabolism benefits seen early on.

References:

Bracco, D., et al. “Effects of Caffeine on Energy Metabolism, Heart Rate, and Methylxanthine Metabolism in Lean and Obese Women.” American Journal of Physiology-Endocrinology and Metabolism, vol. 269, no. 4, 1995, doi:10.1152/ajpendo.1995.269.4.e671.

Graham, Terry E. “Caffeine and Exercise.” Sports Medicine, vol. 31, no. 11, 2001, pp. 785–807., doi:10.2165/00007256-200131110-00002.

Koot, Paula, and Paul Deurenberg. “Comparison of Changes in Energy Expenditure and Body Temperatures after Caffeine Consumption.” Annals of Nutrition and Metabolism, vol. 39, no. 3, 1995, pp. 135–142., doi:10.1159/000177854.

Kruskall, Laura J., and Amy Miracle. “Caffeine And Exercise Performance.” ACSM's Health & Fitness Journal, vol. 13, no. 6, 2009, pp. 17–23., doi:10.1249/fit.0b013e3181bcd865.