Over half of Americans need a little jolt of java or a gulp of red bull to get them going every morning, but have you ever wondered if that caffeine boost helps or hinders your performance in the gym? Does it increase dehydration? How about delaying fatigue? Can you over-caffeinate?

Contrary to popular belief, current research suggests that caffeine is not a diuretic and does not cause dehydration. The US military has done extensive research on caffeine and dehydration and has found that consuming about 100mg/day of caffeine does not increase urine output.

Caffeine may improve performance for endurance athletes (like marathoners and cyclists) and speed endurance athletes (like soccer and hockey players). And as most of us already have experienced, caffeine can delay fatigue and improve mental sharpness. Most exercisers improve their performance by about 12% when using caffeine, however these benefits were only seen for those participating in longer bouts of exercise. Short exercise (8-20 minutes) is not as affected by caffeine and sprinters experienced no benefit. The benefits are greater for those who do not regularly consume caffeine and have not built up a tolerance to its effects.

There are risks involved with caffeine consumption. Some people will experience side effects such as anxiety, nausea, rapid heartbeat, gastrointestinal distress and insomnia.

Don’t forget, caffeine is an addictive substance. When you build up a tolerance to caffeine, the benefits are minimized and withdrawal from caffeine can cause headaches and irritability.

How much is too much?

The amount of caffeine tolerance a person has depends on the individual, but if you are regularly consuming upwards of 500- 600 mg of caffeine per day, it may be time to scale back.


Over the counter pain relievers like Excedrin often contain caffeine (65 mg), as well as weight loss formulas and supplements. Be sure to check the label and add this in to your daily intake. Also be sure to stop wasting your money on any weight loss supplements you might be taking.

Overconsumption of caffeine can lead to restlessness and sleep deprivation. If you think you need to cut back on your caffeine consumption, do so gradually to avoid any side effects of withdrawal. First, avoid any caffeine later in the day then start to cut out one serving of caffeine per day.


Caffeine is absorbed quickly in the body and peaks in the blood about 1-2 hours after consumption. Aim to consume caffeine about 30 minutes to an hour prior to a workout to gain the most benefit.

Keep in mind that black coffee has zero calories but a 16 oz frappuccino has 470 calories and is full of unnecessary added sugar. Even a chai tea latte has about 250 calories. If you choose to get your caffeine before a workout this way, you may be taking in more calories than you burn. Caffeine has not been shown to aid in weight loss.

If you have additional questions regarding caffeine consumption and physical activity or have another nutrition or fitness topic you would like addressed, leave me a comment below or email me at megan@orlandodietitian.tin.