Fuel for Exercise – Part I: Pre-​​Exercise

Fuel for Exercise

We all know that fueling before, during, and after a workout or athletic event is crucial.  In this post, I will talk about fueling specifically before exercise, but keep your eyes out for upcoming posts on fueling during and after exercise.


Hydrating properly is always important as water makes up at least 60% of the adult human body.  Water is vital for removing waste and carrying nutrients to the body’s cells.  We are constantly losing water and fluids through perspiration, urination, and respiration.  These fluids need to be replaced constantly, especially for exercisers, as proper hydration will aid in optimal performance.  Dehydration can cause fatigue, muscle weakness, decreased metabolism, diminished concentration, increased heart rate, and difficulty cooling the body. 

So what and how much should you drink before exercise?  Water is usually the beverage of choice for pre-​​exercise hydration.  Drink enough so that your urine is pale in color.  Urine that appears darker yellow can indicate poor hydration status.  Aim to drink 2–3 ml per pound of body weight at least 4 hours before exercise (one ounce = 30ml), and continue to hydrate by drinking 1–2 cups (8–16 ounces) two hours before exercise, and another 1–2 cups right before exercise. 

Hydration table – example using a 150 pound person

4 hours or more before exercise 300–450 ml (150# x 2-​​3ml/​#) = 10–15 oz (divide total ml by 30 to get oz)
2 hours before exercise 1–2 cups or 8–16 oz
Right before exercise 1–2 cups or 8–16 oz

Is caffeine dehydrating? 
While the common thought is that caffeine is dehydrating, research is now showing that moderate amounts of caffeine (such as the amount found in a 12 ounce cup of coffee) will not have a dehydrating effect.  In fact, caffeine has can have beneficial effects on boosting energy for exercise performance.  So if you love your cup of Joe, go for it!

Pre-​​exercise Fueling

If you are a casual exerciser, doing short bouts of exercise (20 minutes or so), or doing low intensity exercise, you likely do not need extra fuel before exercise.  However, if you are doing longer and/​or more intense bouts of exercise, pre-​​exercise fuel is critical for the following reasons (according to Nancy Clark, MS, RD – a leading sports nutritionist):

  • Preventing low blood sugar and it’s symptoms: fatigue, light-​​headedness, blurred vision, and lack of concentration
  • Fueling your muscles with carbohydrate for both stored energy (glycogen in muscles) and immediate energy.  This also fuels and “feeds” your brain.
  • Settling your stomach and preventing hunger

When you have a pre-​​exercise snack, you will be able to exercise harder, longer, and more effectively, and burn more calories!

When should I eat before exercising?  According to Nancy Clark, in general, large meals should be eaten at least 3–4 hours before exercise, small meals 2–3 hours before exercise, 1–2 hours before exercise for a shake or liquid meal, and less than an hour before exercise for a snack.   However, tolerance to foods and digestion time varies from person to person.  Figure out what works for you through trial and error.

What should I eat pre-​​exercise?  Pre-​​exercise fuel should be mostly carbohydrate.  This is because carbs are used by the muscles for immediate energy, and they empty quickly from the stomach.  High fat foods are not recommended, since they take a long time to digest.

  • If you are exercising for an hour or less – try a banana or other fruit, granola bar, crackers, toast, or pretzels.
  • For exercise >60 minutes, choose carbohydrate with a little protein and fat for sustained energy – try an egg and toast, oatmeal made with low-​​fat milk, yogurt with fruit, or an English muffin with peanut butter.
  • If you are a morning exerciser, try to get a small snack in before exercise for quick fuel – fruit, a small glass of juice, and a granola bar are all good options.

**Remember, eating for exercise is to provide the body with fuel.  If you are working on weight loss or weight maintenance, watch your total calories per day, as always!  Include your pre and post-​​workout snacks/​meals in your daily allotments.**

If you are an athlete and want to learn more about fuel for exercise, I recommend reading Nancy Clark’s Sports Nutrition Guidebook.  More to come soon about hydration and fuel DURING exercise!

- Fuel for Exercise – Part II: During Exercise
- Fuel For Exercise – Part III: Post-​​​​Exercise



  1. John says:

    Good info! I definatly \“bonk\” during some workouts, so hopefully I can better fuel the machine and keep it up throughout my workouts!

  2. Stew Smith says:

    Yes — great article. This advice will definitely help you from \“bonking\” during your workouts. I used to do apple slices and baby carrots before timed runs and swims at BUDS for that extra fuel to push myself.

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Shana Maleeff

Shana Maleeff, M.A., R.D., ACE-GFI, received a B.S. in Nutrition from Penn State University and an M.A. in Nutrition Education from Immaculata University in Pennsylvania. She works in the New York and New Jersey Metropolitan areas counseling clients on nutrition, exercise, medication adherence, and stress management to help them with weight management and treatment/prevention of heart disease and diabetes. Shana is the creator of the groundbreaking weight loss program "The 21 Diet and Exercise Weight Loss Solution". Previously, she worked as a hospital dietitian and as an adjunct professor of nutrition at Philadelphia Community College.

Shana takes a special interest in fitness and works as a group fitness instructor at Crunch Fitness and Equinox gyms in Manhattan. She currently resides in New York City and enjoys living a healthy lifestyle.

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