What to Eat Before Exercising?

What to Eat Before Exercising?

In this article, we present a series of recommendations to optimise your performance when training: what should you eat before exercising?

Why should you eat before exercising?

High-intensity training, especially those with a predominantly mixed bioenergy profile: aerobic-anaerobic (a person training for a sport like CrossFit, a runner doing 400m series, a swimmer training on time for a 200m modality); requires a large amount of available energy to be used quickly, and here what they should eat before practicing a sport becomes important.

The results of the studies are mixed, meaning we can’t draw any firm conclusions about the need to eat before training or not.

It depends on:
  • The type of exercise to be done;
  • The intensity;
  • The duration;
  • The nutritional status of the athlete (that is, if you’ve eaten something before on the same day, what you ate the day before, what you’ll eat after…).

It all influences an athlete’s nutrition!

Discomfort from eating before

Over all, out of 25 studies that evaluated the effects of training on an empty stomach (overnight fasting), or eating before it:

ResultsNumber of Studies Indicating
Better eating than fasting11
Worse eating than fasting0
No difference between eating and fasting14
So, at least we know it won’t do us any harm –and can do us a lot of good.

But, is that right?

Well… De Oliveira and Burini (2011) indicate that some athletes suffer from gastrointestinal discomfort during physical exercise due to previous food consumption.

So what should we do?

Learn what foods and amounts you can include in your pre-workout meal and what you can’t.

And I tell you everything in this article. Want to know more? Keep reading!

Pre-training meal objectives.

The pre-training meal has two main objectives:

  1. Increase the availability of nutrients so that energy can be obtained from them.
  2. Increase the availability of amino acids in the blood to prevent degradation and increase muscle protein synthesis.

Most studies evaluate the effects of pre-training protein consumption from between 30 minutes to 4 hours.

In this article we’ll talk about what to eat 1 hour before training, approximately.


We’ll divide the pre-training food intake into nutrients: carbohydrates, protein, lipids, and water.

Carbohydrates before practicing sport

Carbohydrates are the most important nutrient, and one that must be present in the pre-training nutrition.

This is so because glucose (from carbohydrates) is the nutrient that our body prefers to use for obtaining energy when exercising at a moderate to high intensity.


Because it is denser in oxygen and, therefore, its easier for the body to obtain energy from it (Boron and Boulpaep, 2017).

Which carbs should I eat?

I’ll be direct: from a source that feels good, and, if possible, with a high glycemic index.

It’s best to use a carbohydrate source that has a high glycemic index (speed at which glucose is absorbed and transported into the blood), since the sooner we have it available in the blood, the sooner we can use it.

In addition, any glucose that hasn’t reached the torrent and is still being released into the intestinal lumen, we won’t be able to use.

Simple, right?


My general recommendation is to consume sugar, it tends to suit most people quite well and has a medium-high glycemic index, around 60-80 arbitrary units.


A better option is to consume maltodextrin, especially if the amounts of carbohydrates consumed are higher.

It has a high glycemic index, approximately 80-160 arbitrary units, depending on the degree of polymerisation of the maltodextrin, that is, how long the structure is.


A even better option is to have a highly branched cyclic dextrin.

Because of its structure, glucose is released very quickly into the blood; and because of its high molecular weight, the osmolarity of the drink is reduced, allowing more carbohydrates to be introduced into the same volume of water without discomfort during sport.

Osmotic pressure

Figure I. Relationship between osmotic pressure (X-axis) and gastric emptying time (Y-axis) after the intake of various solutions with 10% carbohydrates. Extracted from Glico.com, adapted by Takii et al., (2005).

Solid Foods

It’s a less accurate option, as the presence of other nutrients in the food matrix can alter the gastric emptying time. Still, if you want to make use of solid food, again: if it feels good, that’s the most important thing that will determine what to eat before training.


  • I would use refined cereals: commercial sweetened cereals are a good choice, creams of rice and/or hydrolysed corn, pasta or white rice boiled for a long time to make it soft; ripe fruits, compotes or jams…
  • I would avoid carbohydrates from oats, brown rice or bread, pulses, etc.

Quantity of carbohydrates

Type of sportCarbohydrate
Resistance1.0 g/kg
Strength0.3 – 0.5g/kg

Figure II. Nutrition recommendations for immediate pre-training. (McDonald, 2007).


The reason for avoiding whole foods is that because of their higher nutritional density they require more enzymatic degradation, meaning more digestion, slower gastric emptying, and more gastrointestinal discomfort, without really giving us any benefit at this time of day.

Fibre has important health benefits, especially related to:

  • maintaining microbiota health
  • increasing faecal mass and improving intestinal transit;
  • slowing down the absorption of nutrients in the small intestine;
  • increasing satiety;
  • having potential as coadjutant treatment in diabetics, cardiac patients, the obese, etc. (Dreher, 2018).
However, slowing down gastric emptying at this point is not in our interest at all, or do you want to train on a full stomach?

Proteins before practicing sport

Proteins are an important nutrient for training as they’ve been shown to be effective in increasing protein synthesis and preventing muscle mass degradation, i.e. they are a powerful anabolic/anti-catabolic.


Consuming the protein before or after training is irrelevant, as both lead to the same gains in muscle mass (Schoenfeld et al., 2017), which is why you can do this:

Did you make a protein meal three hours ago or less?

  • Short training (~1 hour): take it post-training
  • Long training (1h 30m): take it intra-training

Haven’t had a protein meal in the last three hours?

  • Consume protein pre-training.

Where do I get this protein from?

Once more: from a source that makes you feel good. And ideally from a quick absorption source.

Absorption of amino acid protein is independent of the presence of other nutrients, and is determined by the type of protein in the food you eat.

Remember: the protein in milk is different from that in chicken, or eggs, and therefore its absorption is also different.

I’ll leave a table for you to see the protein absorption rate per hour depending on the source:

Source of proteinRate of absorption (g/hour)
Raw egg protein1.4
Cooked egg protein2.9
Pea protein3.5
Milk protein3.5
Isolated soya protein3.9
Whey protein isolate8-10

Figure III. Ratio of protein absorption from different sources (McDonald, 2007).

It would also be advisable to avoid foods that, although their absorption may be fast (such as pork), contain a high amount of fat, as this fat, although it doesn’t affect the absorption of protein, does affect the absorption of carbohydrates, slowing it down, and that is something we do not want.

In this post made a comparison of the best proteins to eat before training.

Proteins from supplements

Pre-training is the ideal time to consume a whey isolate, and if it’s hydrolysed, even better.

If we have gastrointestinal problems, it’s better to use Peptopro® with 2 grams of leucine added.

Or alternatively, a source of essential amino acids or BCAAs.

Protein from solid food

If we do decide to eat a whole food, we’ll choose a source that we know we can tolerate very well, preferably a lean one:

Cooked egg whites > Skinless chicken > White fish

Quantity of protein

Type of sportProtein
Resistance0.15-0.25 g/kg
Strength0.32 – 0.55g/kg
*If you’re going to use free amino acids (EAAs/BCAAs) in a strength sport, use half of the recommendation.

Figure IV. Nutrition recommendations for immediate pre-training. (McDonald, 2007).

Fats before practicing sport

Fats are an incredible source of energy, but unless the physical exercise you are going to do is at a very very low intensity, or you’re terribly adapted aerobically (marathon runner, cyclist, triathlete…), I would stay away from fats in this intake, it’s not the time.

Some authors and sports nutrition experts recommend including a small source of fat to avoid a sudden switch to glucose in the blood and to prevent reactive hypoglycaemia.


But this is a picture that will never be seen in a person who is metabolically healthy, so I completely disagree with this argument.

Consuming fats can alter the speed of gastric emptying of carbohydrates, causing them to be absorbed more slowly, and increasing the gastric load.

Where do I get these fats from?

If you decide to make use of the fats, it would be interesting to move the pre-workout intake a little further away, at least to the hour and a half – 2 hours mark, depending on the amount of fat you consume.

Among all the sources, I would choose coconut or palm oil, which contain fatty acids in the form of medium chain triglycerides that do not require passage through the lymphatic system and go directly to the liver through the carrier system, to be used quickly as energy. In other words, they’re more efficient (Babayan, 1981).

Quantity of fats

Type of sportProtein
Strength<0.05 – 0,.1 g/kg

Figure V. Nutrition recommendations for immediate pre-workout.


Though it doesn’t give you energy, drinking water before practicing sport is important.

One of the main routes of liquid elimination in the human body is through sweat.

And even mild dehydration of about 2-3% can seriously affect sports performance. Dehydration of 7-10% puts a person’s life at risk, when it can become lethal (Grandjean et al., 2003).

Drink water

When we get dehydrated to around the 3% mark, we become thirsty, an unmistakable sign that we have to drink.

But athletes perceive this sensation late, which makes it important to prevent it by ensuring a sufficient pre-training water intake.

Quantity of water

5-10 ml / kg of body weight between 2 and 4 hours before physical exercise (enough to be able to urinate the excess water consumed), until reaching a pale yellow urine colour (ACSM, 2016).

Hydrating before training

Other important nutrients to consume despite not being energy sources include: mineral salts (electrolytes) in our pre-workout drink so as not to alter the electrolyte balance of the body’s internal environment.

And we should pay special attention to sodium, chloride, and potassium; and to a lesser extent to calcium and magnesium too.

Sodium is the most important, not only because its concentration influences intestinal absorption of glucose (important so that you don’t suffer malabsorption and feel discomfort), but also because it is the main osmolite that regulates plasma volume. That’s to say, the more sodium, the more water we retain.


And since we’re going to be exercising, we’re interested in retaining water, right? 😉

Quantity of electrolytes

We don’t know the exact amount of electrolytes that we should consume because it depends on factors such as the amount of liquid that we eliminate through sweat, or the concentration of this, which depends on factors such as the environment, the type of physical exercise, our sweat rate, the state of hydration …

I recommend ensuring the consumption of 460mg of sodium for every litre of water consumed.

Summary of Pre-Training Nutritional Recommendations

Pre training nutrition

Bibliographic Sources

  1. Aird, T. P., Davies, R. W., & Carson, B. P. (2018). Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis. Scandinavian Journal of Medicine and Science in Sports, 28(5), 1476–1493.
  2. Babayan, V. K. (1981). Medium chain length fatty acid esters and their medical and nutritional applications. Journal of the American Oil Chemists’ Society, 58(1), 49A-51A.
  3. Boron, W., Boulpaep, E. (Eds.) (2017). Medical physiology: a cellular and molecular approach Philadelphia, PA: Saunders/Elsevier.
  4. De Oliveira, E. P., & Burini, R. C. (2011). Food-dependent, exercise-induced gastrointestinal distress. Journal of the International Society of Sports Nutrition, 8, 12.
  5. Dreher M.L. (2018). Dietary Fiber in Health and Disease. Nutritiοn and Health. DΟI: 10.1007/978-3-319-50557-2.
  6. Grandjean, A. C., Reimers, K. J., & Buyckx, M. E. (2003). Hydration: Issues for the 21st century. Nutrition Reviews, 61(8), 261–271.
  7. Latzka, W. A., & Montain, S. J. (1999). Water and electrolyte requirements for exercise. Clinics in Sports Medicine, 18(3), 513–524.
  8. McDonald, L. (2007). The Protein Book: A Complete Guide for the Athlete and Coach. S.D.: Lyle McDonald.
  9. Morris, D. M., Huot, J. R., Jetton, A. M., Collier, S. R., & Utter, A. C. (2015). Acute sodium ingestion before exercise increases voluntary water consumption resulting in preexercise hyperhydration and improvement in exercise performance in the heat. International Journal of Sport Nutrition and Exercise Metabolism, 25(5), 456–462.
  10. Qi, X., Al-Ghazzewi, F. H., & Tester, R. F. (2018). Dietary Fiber, Gastric Emptying, and Carbohydrate Digestion: A Mini-Review. Starch/Staerke, 70(9–10), 1700346.
  11. Sands, A. L., Leidy, H. J., Hamaker, B. R., Maguire, P., & Campbell, W. W. (2009). Consumption of the slow-digesting waxy maize starch leads to blunted plasma glucose and insulin response but does not influence energy expenditure or appetite in humans. Nutrition Research, 29(6), 383–390.
  12. Schoenfeld, B. J., Aragon, A., Wilborn, C., Urbina, S. L., Hayward, S. E., & Krieger, J. (2017). Pre- versus post-exercise protein intake has similar effects on muscular adaptations (J. Keogh, Ed.). PeerJ, Vol. 2017.
  13. Takii, H., Takii, Y., Kometani, T., Nishimura, T., Nakae, T., Kuriki, T., & Fushiki, T. (2005). Fluids containing a highly branched cyclic dextrin influence the gastric emptying rate. International Journal of Sports Medicine, 26(4), 314–319.
  14. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise, 48(3), 543–568.

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Review of What to Eat Before Exercising

Protein recommendation - 100%

Carbohydrate recommendation - 100%

Fat recommendation - 100%

Fibre recommendation - 100%

Hydration - 100%

Supplements - 100%


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About Alfredo Valdés
Alfredo Valdés
A specialist in Pathophysiology and biomolecular effects on nutrition and sportive activity who will show you the elaborate world of sports nutrition in his articles, employing a simple and critical writing.
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