Coffee and training: a dehydrating or stimulating pair?

Food and nutrition

Published on 8 March 2014
by Isabelle Huot

If you think drinking coffee before working out can dehydrate you, you might want to think again! Surprisingly, whether you drink a glass of water or a cup of coffee, your body will produce the same volume of urine. Studies show that the diuretic effect of caffeine is null to none if you drink a moderate amount of coffee (≤ 3 to 4 cups of coffee per day).

Drinking coffee could even have some positive effects on your work out! Caffeine can stimulate concentration, decrease fatigue, and increase the ability to initiate an effort, prolong the endurance time of the effort and increase fat burning during the effort, thus allowing preserving glycogen stocks. To get to potential benefits, it is recommended that you take 2 to 3mg of caffeine for each body weight kilogram, 30 to 90 minutes before working out. This represents approximately 200mg of caffeine, or two cups of drip brewed coffee.

However, all individuals do not respond the same way to caffeine. Caffeine can sometimes cause secondary effects such as palpitations, irritability, anxiety, and shivering, sleeping problems and drop in energy.  And so, before working out, ensure you drink your coffee along with eating a low glycemic index snack, such as a granola bar, a yogurt or a fruit. Also, not knowing the effects caffeine will have on you, you might want to test the resulting effects during a workout instead of a competition. 

Isabelle Huot
Doctor in nutrition, spokesperson for the Kilo Cardio weight loss program