Healthy Habs, No Diets

To eat or not eat before exercise?


To eat or not eat before exercise

This is a question that my patients ask me a lot, that’s why I dedicated this article to you, and this is my answer:

EAT before exercise

That’s right, I recommend to eat that pre-workout depending on the type of exercise you do. And by saying pre-workout, I DON'T mean those liquids with caffeine or with stimulating substances.

Previously it was believed that, if you fasted or if you did NOT eat before exercise, it would be a greater calorie burn, because if you make exercise after fasting for 7 to 8 hours (the hours you were sleeping), your body will first obtain energy from the stored carbohydrates (in form of glycogen) in your muscles and liver. Once your glycogen reserves are finished, your body will start to burn the stored fat.

If you are trying to burn fat, exercising with an empty stomach seems to make sense: Without calories in the tank, your body starts to burn the fat reserves, right?

But this is not that simple. One of the reasons that I’m not in favor of fasting is that your body perceives fasting as a stressor, and that causes the release of cortisol, that leads your body to break the muscle to use protein as fuel.

Doing cardio in a fasting mode can increase fat oxidation and use it as energy, but, unfortunately, it can also lead to protein degradation, which is not a very good thing. The less muscle, the lower your metabolic rate.

Why should I eat before exercise?

It is probably, that eating a pre-workout can reduce the burning of fat during exercise, but the good news is that your body not only burn exercise during training, it can also burn fat after exercise! This happens due to a phenomenon known as excess oxygen consumption post-exercise. We can continue burning calories from a few minutes up to 24 hours after exercise. But put closely attention to this: The more intense the exercise, the longer the duration of post-exercise fat burning.

So consume a snack before exercise that will serve you as fuel in order to complete the entire routine and for not feeling fatigued due to the depletion of your glycogen reserves. Having energy during training will make you gain condition and strength, so every time you make higher intensity exercises, it will help you burn many more calories post-exercise.

Don’t stop making exercise, it is a very important factor for maintaining us in a healthy weight, since we can burn calories during and after exercising, each time we will be able to use more fat as energy.

What if I don’t want to consume a pre-workout snack?

It is common for many people for not having hungry an hour or half an hour before a routine. They feel that "they are going to throw up the food during the exercise" (this is how they express it to me).

The type and time of exercise defines whether the pre-workout snack is NECESSARY or OPTIONAL.

When a snack is required before exercise, and when it is optional

If you make low to moderate intensity exercise for less than 90 minutes (1 hr and 30 min), the pre-workout is OPTIONAL.

By saying low-moderate intensity exercises I refer as walking or jogging at the same pace, Zumba, restorative Yoga, among others.

If you make low to moderate intensity exercises for less than 90 minutes, for your body is easier to convert fat into energy, and you can do an excellent routine without the necessity of eating a pre-snack.

The majority of people has sufficient glycogen for fueling their bodies during exercise, and the fat is also being mobilized and burned at a faster rhythm compared to carbohydrates in the same low intensity exercise.

If you make high intensity exercise, the pre-workout is NECESSARY. DO NOT FAST.

If you are doing high intensity exercises, your performance will suffer a lot if you don’t consume a previous snack. It’s not possible to mobilize and burn the fat reserves during higher intensity exercises to provide stable fuel for your body. Once your body is out of carbohydrates, it would not keep working at the same intensity.

Also, if you finish your intense training without eating something previously, you will feel very tired and the risk for eating in excess during the day will increase.

My recommendation

If your goal is to lose fat and at the same time to maintain your muscle, you will need to consume a snack before exercise.

But the most important thing (and I will write it down in bold): Always use common sense to decide whether eat or not eat before exercise.

I think it’s best to use your common sense and to listen to your body. If you made exercise with an empty stomach and during the training you felt tired or with nausea (even though you have done less than 90 minutes of exercise), you WILL NEED to eat a snack previous to exercise.

What are the best pre-workout snacks?

If you decide to eat before exercise, then I recommend these delicious snacks. Save this images in your phone, so that you have the options of snacks at hand depending on the exercise you want to do.

These snacks are recommended to be consumed from 30 minutes up to 1-2 hours before performing your routine.

Now I present to you, the best snacks depending on your exercise routine, whether you lift weights, do Crossfit, HIIT, yoga, running, and among any more exercises. I have snacks for almost all types of exercise.

Pre-workout: Weight training in the morning

Dinner helps you fill your glycogen stores: Complex carbohydrates + vegetables + lean protein

30 min - 1 hour before your workout, consume a light snack and easy to digest that will help you fill your glycogen reserves at the moment, for example, a snack with high content of simple carbohydrate of low-moderate glycemic index.

Pre-workout: Weight training in the afternoon

A snack 2-3 hours before your weight training in the afternoon, helps you fill your glycogen reserves and gives you energy in a prolonged way: Complex carbohydrates + vegetables + protein

Pre-workout: Yoga or pilates

30 min - 1 hour before your Yoga or Pilates class eat a light and easy to digest snack with high content of simple carbohydrate of low-moderate glycemic index.

Pre-workout: Hot Yoga

1 hour before your Hot Yoga class eat a light easy to digest snack with high water content to keep you hydrated and energized.

Pre-workout: Cardio in the morning

1-2 hours before your morning cardio eat a light easy to digest snack.

Pre-workout: Cardio in the afternoon

1 hour before afternoon cardio, eat a light easy to digest snack with high water content to keep you hydrated and energized.

Pre-workout: Climbing

1 hour before climbing, eat a snack that helps you maintain energy in a prolonged way: complex carbohydrates + simple carbohydrates + healthy fats with protein.

Pre-workout: HIIT

1-2 hours before your HIIT (High Intensity Interval Training), consume a snack that helps you conserve energy in a prolonged way to resist intense exercises: high in complex carbohydrates + simple carbohydrates + protein.

Pre-workout: Crossfit in the morning

1-2 hours before your Morning Crossfit workout, consume a snack that helps you conserve energy for a long time: Protein + complex carbohydrates + healthy fats

Pre-workout: Crossfit in the afternoon

1-2 hours before your Crossfit training in the afternoon, consume a snack that helps you conserve energy in a prolonged way: Protein + complex carbohydrates + healthy fats.

Pre-workout: Endurance Training

1 hour before from your endurance training (Running 10, 15 km or a triathlon), consume a snack that helps you conserve energy in a prolonged way and at the same time avoiding insulin spikes: Fiber + healthy

Don’t forget that if you perform more than 1 hour, you need to consume a little bit of simple carbohydrate during training: Fill your bottle with natural mango water (or other fruit) with 1 tablespoon of honey.

Referencias Bibliográficas:

Aziz, A. R., Wahid, M. F., Png, W., & Jesuvadian, C. V. (2010). Effects of Ramadan fasting on 60 min of endurance running performance in moderately trained men. British Journal Of Sports Medicine, 44(7), 516-521. doi:10.1136/bjsm.2009.070425

Bouchard, C., An, P., Rice, T., Skinner, J. S., Wilmore, J. H., Gagnon, J., & ... Rao, D. C. (1999). Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study. Journal Of Applied Physiology (Bethesda, Md.: 1985), 87(3), 1003-1008.

Leigh, D. (s.f.). Best Protein to Eat Before Every Workout. Recuperado el 9 de septiembre del 2017, de:

Martín, M. (s.f). Aerobic y Fitness. Fundamentos y Principios básicos. España: Librerías Deportivas Esteban Sanz, S.L.

Men´s Fitness. (s.f.). “Should you work out on an empty stomach?”. Recuperado el 9 de septiembre del 2017, de:

Morales, J.A. (2010). Obesidad un enfoque multidisciplinario. México: Universidad Autonoma del Estado de Hidalgo

Schoenfeld, B. J., Aragon, A. A., Wilborn, C. D., Krieger, J. W., & Sonmez, G. T. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal Of The International Society Of Sports Nutrition, 11(1), 54. doi:10.1186/s12970-014-0054-7

Stannard, S. R., Buckley, A. J., Edge, J. A., & Thompson, M. W. (2010). Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state. Journal Of Science And Medicine In Sport, 13(4), 465-469. doi:10.1016/j.jsams.2010.03.002


Soy Giselle, nutrióloga mexicana, viviendo en Texas. Floja para la cocina y práctica para el ejercicio.


En este blog encontrarás recetas rápidas y prácticas, utilizando ingredientes básicos. También productos que recomiendo de H-E-B.

Y por último, encontrarás artículos y opiniones con enfoque no-dieta y no-peso para que nunca más vuelvas a seguir una dieta ni a darle importancia a la báscula.

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