Sunday, January 16, 2011

Pre-Workout: To Eat or Not to Eat...

That is a question that lots of people have.  And for everyone that asks there are at least three people waiting to give their 'expert' opinions.  Before the question gets answered let's take a look at each side...

The "Empty" Exercises:
This group claims that working out on an empty stomach is the best way to burn fat.  They argue that if carbohydrate (glycogen) stores are empty then the body has no choice but to use fat for energy.  Are they right?? 

Well... When you exercise without eating it does increase the amount of fat broken down in the muscles.  So you may improve how the muscles burn fat, but unfortunately this will not affect overall body fat.  It may be possible that more intense exercise could stimulate the burning of fat in other areas of the body - but it would take quite a bit of training to see significant results.

The First-Thing 'Fuelers':
This bunch says eating prior to exercise provides the energy and fuel necessary to perform optimally.  This may be especially true when training first thing in the morning or following an extended period without food.  The body has a limited supply of glycogen, (the storage form of carbohydrate), in the liver and muscles. Even though the body may have plenty of fat to use - it can't be burned in the absence of some glucose - more specifically, ATP (the first step of fat breakdown (oxidation) is an energy requiring reaction).  When you go into a workout with an empty tank results in depleting the body's energy stores completely.  This may result in a less intense workout (therefore you will burn fewer calories) or 'bonk' (trust me - you don't want to do it). 

So, you might be asking, where did the energy to get me through my workout come from?  It gets a little complicated here.  It may be that your body entered a state of ketosis or a 'starvation' mode.  What that means is fat starts being used for energy.  That's good right?  Well, yes and no...  Ketosis is not an 'efficient' process.  It doesn't happen immediately, may result in muscle loss; and since it's a survival mechanism, causes a drop in metabolic rate.  Also, most people tend to 'overcompensate' on food intake later to plug the hole.  So the net result ends up being a less than optimal workout, decreased metabolism, loss of muscle, and overeating.  Additionally, exercising empty results in prolonged recovery time and potentially, a cruddy next workout.

The Verdict:
A recent study, published in the International Journal of  Sport Nutrition and Exercise Metabolism, compared energy/fat utilization markers (VO2 - oxygen consumption) and (RER - respiratory exchange rate) in fasted versus fed athletes. The VO2 and RER levels in the pre-workout eaters were greater than that of those in the fasted group at all measured intervals (during exercise, as well as 12 and 24 hours post-workout).

Ultimately the choice is yours; you've got some facts - granted there's also stuff out there claiming the opposite.  My advice is this - if you're serious about performance and if recovery counts, definitely do not go in 'empty'.  In the event you do decide to take the fasted approach don't expect to see the fat just 'melt' away, have your best workout, or recover quickly and optimally.  Your meal doesn't have to be huge - some carbohydrate to fuel your muscles, a little protein to preserve them, and possibly a bit of fat to keep your stomach from growling if you're going long.  And remember, you have to "Eat to Compete"!!



  1. It depends on your goals. An endurance athlete will want to use fasted workouts when doing long, lower intensity base-building workouts to improve the ability to burn fat as fuel. But higher intensity workouts demand more prefueling for performance and recovery.

    If you are just trying to lose weight then fueled, more intense workouts may be a better options to boost metabolism. No two bodies are alike and the science only points to what works on average. We all have to experiment and see what works for us.

  2. Anonymous -

    By nature LSD training results in using a higher percentage of fat for energy whether fasted or fed. As the intensity of the training increases fat utilization decreases and carbohydrate supplies the bulk of the energy. For an endurance athlete the pre-workout meal is important in order to prevent muscle breakdown and/or "hitting the wall" during the long training session. Additionally research has shown that athletes are able to 'go longer' when they have either eaten prior to or during a long training session. The pre-workout meal also minimizes the deficit that results from a training session and helps to shorten the recovery period.

    I completely agree with you in that we all need to experiment in order to find out how our bodies run best. Based on the experience and feedback of the endurance athletes I work with - the pre-workout meal is a go.

    Thanks for the comment!

  3. So I train both in the morning (empty stomach currently) when a pre-workout meal would be 5-15 minutes before a session and in the afternoon when eating 2 hours out is not a problem and my personal preference.

    For higher intensity sessions and/or weight training sessions in the AM with little lead time, what might be some options to provide carb, protein and fat? Gel and maybe some nut butter? Powerbar? Would your answer change for LSD training under the same time-crunched scenario?

    Can you also comment on the same question with a 1-2hr pre-session lead time for both low and high intensity training? Currently, I'll go with an apple and 1-2TB nut butter 2hrs before a lower intensity prep/base session.


  4. I've tried both ways to see how my body reacts. If I workout on an empty stomach, I feel drained and weak. My workouts are substandard and I often feel like I'm "wading through water." When I eat only protein and or fat, I have more energy and can complete the workout. However, when I add some carbs into the mix, my times are better, I feel stronger and I don't feel the need to eat for hours after the workout. I've tried eating carbs the night before and it hasn't made any difference. I have to eat at least one hour before working out - any sooner than that and I feel sick to my stomach when I push really hard. That much makes sense to me, though! :)

  5. Good post! I think it's also important to view the overall diet when looking to this answer. I think of the muscles and liver as fuel tanks. Combined, they can store roughly 500g of carbohydrate. Hypothetically if those were full--perhaps someone on a moderate carbohydrate diet who's limiting the amount of time they spend in glycolytic activity--it'd be hard to imagine a scenario where all 500g were depleted overnight. Even fasted, they should have enough fuel in the tank to perform well on a reasonable workout. Something like BCAAs pre-workout might be enough to preserve muscle.
    Conversely take someone on a lower carbohydrate diet or who frequently does depleting workouts, if when they go to bed their fuel tanks are only partly full, then they will of course be even more depleted in the morning.

    Also important to note that it can take roughly 6 weeks to adapt to a lower carbohydrate/higher fat diet, which in some ways is similar to fasted training, so a lot of these studies that are shorter than 6 weeks are not always applicable to someone who's already been fat adapted.

    Also, what's your stomachs tolerance of the pre-workout meal? does the athlete get the trots, nausea, or frequently meet pukie?

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