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Caffeine-- The Do's & Don'ts

Did you know about 90% of the world's population consumes caffeine daily?? As a 10%er I can definitely see this being accurate because when I tell someone I don't drink coffee they are shocked. As a mom and an early morning runner you would think this would be a necessity. Truth is-- it doesn't make me feel good. I feel jittery and can't focus so I avoid it.

As a Dietitian that works with active individuals, caffeine is a topic that comes up A LOT. Some of the most common ways I see it being used are:

  • As a pre workout supplement

  • To get your day started or as a mid day pick up

  • In endurance events like ultramarathons

  • In place of breakfast

Let's chat about some of the do's and don'ts when it comes to using caffeine in your daily life and in training


Caffeine as a pre-workout

Caffeine is an ergogenic aid which basically means it has been shown to enhance performance. When taken in doses of 3-6mg/kg 60 minutes prior to exercise it has shown a 2-4% improvement in endurance. If you are using a pre workout powder or drink be sure to check the labels as these often have WAY more caffeine than is recommended. I don't recommend these drinks to begin with but if you're going to drink them be sure you know how much you're consuming and cut back on the dosage if needed.

The timing of caffeine is important because it peaks in your system around 60 minutes. If you're heading to the gym for a 60 minute class and you consume caffeine right before you head in, you're going to miss out on those performance improvements. It's also important to know that caffeine does not create energy--only food does that. Caffeine blunts the feeling of fatigue but it doesn't actually give you more energy. If you're only consuming caffeine before your workout I recommend pairing it with some quick acting carbs like a piece of fruit, frozen waffle, toast, bagel, graham crackers, etc.. Caffeine on an empty stomach can spike cortisol levels which can have negative impacts on your health.

Caffeine during endurance events

Many endurance athletes utilize caffeine as part of their fueling strategy especially in events that last 24+ hours. Just like with that pre-workout dose of caffeine, the timing is important. The most common times that caffeine is used include: before a race with an early morning start time, before a known tough part of the course to get an edge, and overnight when your body is telling you it's time for bed. Dosage is important too because more is not better. Your goal should be to determine the minimum amount of caffeine needed to see that performance improvement. General guidelines are: no more than 72mg/90 minutes

Caffeine on a daily basis

Caffeine blunts your appetite which means if you're waking up in the morning and the first thing that you consume is your coffee, you may not feel very hungry. I think this is a BIG reason that a lot of people that I work with for 1:1 nutrition coaching skip breakfast. This habit then often leads to underfueling during the day when you need food/energy the most and over eating later in the day. I'm not saying to give up your coffee but be sure that you are drinking some water and eating something before you do--your body will thank you. Caffeine has the tendency to disrupt sleep as it has a half life of about 5 hours. It's easy to get sucked into the cycle of poor sleep (because of high caffeine consumption) that then requires--you guessed it--more caffeine to be able to function.


Kayla Fitzgerald is a Registered Dietitian & Certified Intuitive Eating Counselor and founder of Endurance Nutrition located in Charleston, South Carolina. She works with clients 1:1, through small group coaching, and self guided programs. Her goal is to help you fuel your body for whatever the day has in store whether it's a 100 mile race or getting through the work day.


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