To eat or not to eat before exercise - what's the evidence?

[this_dot]

TL;DR​

Performance should be similar between fed and fasted state, except for high-duration aerobic exercise (where eating low GI carbohydrate is advantageous).

There appears to be more muscle adaptation and free-fatty acid utilization when exercizing fasted.

Should we exercise fasted? Should we eat before? What? How much?

These are questions I’ve seen asked around here a lot, and decided to search the literature. I guess this can be a controversial topic, as there are many strong opinions out there in the fitness community. There should be a lot of individual variation and each of you may feel better exercising fasted or after eating, and it’s probably fine either way.

First, I’ll present the conclusions of a 2018 systematic review by Aird et al:

Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis.

Performance​

There appears to be a beneficial effect of eating before a prolonged (>60min) aerobic activity (mainly using low/moderate GI carbohydrate meals – a quick list for you, here).

For short duration aerobic activity, 57% of the studies found no difference between fed or fasted state.

There’s less evidence available for anaerobic exercise. One study found benefit of a carbohydrate meal before anaerobic exercise (improved time to exhaustion). Three studies found no difference before HIIT.

Metabolism​

Fasted exercise mobilizes and promotes free-fatty acid utilization.

Regarding muscle adaptation, here’s the authors conclusion:

Fasted training activates signaling pathways which beneficially regulate metabolic adaptations in skeletal muscle, whereas preexercise feeding abrogates such effects. However, significant literature gaps remain regarding this topic.

Some studies on overweight, inactive individuals, showed less differences between fasted and fed state exercise.

Other recent studies​

After the publication of the review above, there have been many more studies. I’ll just present the conclusions of a few.

Other review, by Wallis et al 2019 concludes:

…there is evidence that overnight-fasted exercise in young, healthy men can enhance training-induced adaptations in skeletal muscle metabolic profile

Kondo et al, 2019 found that transient hypoglycemia after preexercise CHO ingestion occurs in some, but not all, subjects and subjects with enhanced insulin responses seem to be more prone to transient hypoglycemia in the fasted condition.

Kotopoulea-Nikolaidi et al, 2019 tried to evaluate psychophysiological responses and found the following:

if this type of exercise (HIIE) is supported by high carbohydrate pre-exercise feedings such as the typically prescribed high carbohydrate breakfast 2–3 h prior to exercise and a carbohydrate sports drink immediately prior to exercise, it can lead to improved mood, exercise engagement and possibly greater exercise tolerance.

Conclusion​

There’s much evidence that benefits exercising fasted for metabolic reasons. I assume there should be a lot of individual variations, and it’s not clear if these differences will be persistent for long periods of training or if they’re noticeable in practice.

There’s some research with protein intake instead of carbohydrates, but it’s still very little.

It appears to be an increasing interest in this topic, so I hope there’s more and more information appearing in the near future.

What do you guys prefer? Can you see any noticeable difference in performance either way?

References​

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 & Science in Sports, 28(5), 1476–1493.

Kondo S, Tanisawa K, Suzuki K, Terada S, Higuchi M. Preexercise Carbohydrate Ingestion and Transient Hypoglycemia: Fasting versus Feeding. Med Sci Sports Exerc. 2018;51(1):168-173.

Kotopoulea-Nikolaidi M, Watkins E, Giannopoulou I. Effects of High Carbohydrate vs. High Protein Pre-exercise Feedings on Psychophysiological Responses to High Intensity Interval Exercise in Overweight Perimenopausal Women. Front Nutr. 2019;5:141. Published 2019 Jan 22. doi:10.3389/fnut.2018.00141

Wallis, G., & Gonzalez, J. (2019). Is exercise best served on an empty stomach? Proceedings of the Nutrition Society, 78(1), 110-117. doi:10.1017/S0029665118002574

 

[dawn16]

@this_dot Good stuff. I personally think it really depends on the person.

When I started doing ultra distance cardio events (ultrarunning, mountaineering) people would tell me "Carb up the night/morning before dude!"

And I'd eat a huge ass bowl of pasta and breaksticks and anything else I could shove down because I knew I would eventually "need it".

It never helped even a little bit

 

[hannahjoy]

@dawn16 That's because you were basically eating sugar.

 

[justg]

@dawn16 What do you do now?

 

[dawn16]

@justg Small balanced breakfast and eat a handful of something every 30-60min

 

[this_dot]

@dawn16 Nice testimony! Thanks.

What do you prefer to eat? Or doesn't even matter?

 

[betaninja]

@this_dot nunped killing it with another excellent post. Motivated to post my own on a meta-analysis of training frequency that someone sent my way yesterday.

I've gone from exercising fasted to doing a whey isolate shake (switched to skim milk from water) before I exercise. I was exercising fasted when I was cutting because I find restricted eating intermittent fasting to be a great way for me to control my energy intake.

Can't say that I've noticed any difference in what I can do. I have hit a plateau in both pullups and rows, which I would love to blame on the protein shakes, but they're more likely both bottlenecking because of weakness in my back.

 

[this_dot]

@betaninja

because I find restricted eating intermittent fasting to be a great way for me to control my energy intake

This is a personal preference that can actually be helpful for a lot of people!

 

[baristaben]

@this_dot If I eat before exercise, I'll get some kind of abdominal pain unless what I'm doing is really light. I simply can't train the same way and at the same intensity when I've just eatien.

 

[cbsmel]

@this_dot In my opinion, the only evidence is personal experience. It doesn't matter what the studies say, I always perform better when I train fasted.

 

[thehealer]

@cbsmel Same here. I cramp up otherwise.

 

[leonidas157]

@cbsmel And I always perform better if I had a good meal a couple hours earlier. It's not about physical performance though, but rather determination to push myself further.

 

[cbsmel]

@leonidas157 exactly.. it just depends on person to person.

 

[sng092]

@cbsmel I agree that going by how you feel is importiant, but part of your post is like saying

"who cares what the studies say on global warming. All I know is that its cold outside right now!"

Don't disregard scientific literature, when used properly its the highest quality of information you can find. Anecdotes are simply to act as support for what the science says and are for filling in the gaps when the scientific community has no good consensus.

 

[cbsmel]

@sng092 Working out and global warming are completely different issues.

 

[sng092]

@cbsmel You cant cherry pick which subjects you apply science to.

Science must be intimately involved in how you work out for optimal training. To disregard the science of exercise is to open the door for ineffective training.

 

[cbsmel]

@sng092 lol I am not disregarding science. Your comment does not make any sense! I like to work out fasted and it fits my schedule. I am not going to change my schedule just because some studies show something else. The only time I can workout is morning 4:30 am to 6:30 am. I am not waking up at 3 am just so that I can train in a fed state just because science tells me to do so.

And as far as global warming is concerned, it is a global issue which affects everyone on earth. My working out fasted vs fed is my personal issue and no one else in the world gets affected with this.

Use some common sense ffs

 

[sng092]

@cbsmel

ol I am not disregarding science.

yet in your previous comment you said...

In my opinion, the only evidence is personal experience. It doesn't matter what the studies say

Pretty contradictory.

Your comment does not make any sense!

Just because you don't understand the comment doesn't mean that the comment doesn't make sense.

I am not going to change my schedule just because some studies show something else.

You don't have too, but if solid scientific evidence (not pseudoscience or bad studies) say that something else is better, it would be wise to at least acknowledge that "yes I realize that something else is better and what im doing is not optimal"

The only time I can workout is morning 4:30 am to 6:30 am. I am not waking up at 3 am just so that I can train in a fed state just because science tells me to do so.

I'm not arguing against fasted training so that point is moot.

And as far as global warming is concerned, it is a global issue which affects everyone on earth. My working out fasted vs fed is my personal issue and no one else in the world gets affected with this.

if you want to talk about comments that make no sense... here we are.

Science affects personal issues just as much as it effects global issues. Science is everywhere and affects everything.

 

[cbsmel]

@sng092 I never said that fed workouts are bad.. I said it is a matter of personal preference.

 

[sng092]

@cbsmel

I never said that fed workouts are bad

I never did either.

I just said that one shouldn't value anecdotes over science and nothing more.