Caffeine can boost athletic stamina and speed so much that the International Olympic Committee once limited how much of it Olympic athletes could take. Caffeine was categorized as a performance-enhancing substance.
The regular athlete might not be able to run a marathon in 2:02.57 like Dennis Kimetto, but maybe after an invigorating jolt of java you can one run just a little bit quicker and burn some fat in the process. Caffeine can improve performance by 1.5 to 3 percent, recent studies show. And the amount needed to give the boost is no more than that in an 8-ounce cup of coffee or an energy drink or two.