Whether to Eat Before or After Running (or other exercise)

Question:

Is it better to eat before or after exercising?
How soon after eating is it okay to run?

P. Mark’s Answer:

You can eat before or after.  It depends on what your eating and how long it takes to digest.  Typically, your body takes about 3 hours to fully digest a large meal.  A small meal can be digested in as little as 2 hours.

The consequence of this: if you eat a meal of any size, you should wait at least 2 hours before challenging your body.  If the exercise is extremely light and easy for your body, it might be just fine.  Anything beyond that requires serious resources from your body.

Problem 1:  Your body fluids can’t be in two places at once.  Extra blood gets routed to the area of your gastrointestinal system so that it can absorb and deliver the incoming nutrition.  Digestion also diverts some of the water in your system to that process.  These combine to yield a significantly lower flow of blood to your muscles.  If you go fast enough that your body prioritizes the exercise over digestion, then you have other problems.  You could feel some cramping in your GI system.

Problem 2:  Heavy jostling leads to poor digestion.   It is too difficult for the nutrition to be absorbed effectively when it is swishing around.  Hence, you are getting less from your food.  This also requires that diversion of fluids to remain in effect longer.

Possible Results:  Poor Performance, cramps, &/or indigestion.  At the very least, it slows you down a little and you may have wasted some valuable nutrition.

What you CAN eat before a run or other exercise:  A small amount of simple carbohydrates can be eaten (or drank) within one hour of exercise.  That is what energy gels are designed to do: provide a blend of simple sugars and slightly more complex sugars to be used immediately by the body.

Remember This!

If you have been eating relatively healthy and in sufficient quantity,
your body has a supply of energy waiting to be used!

Glycogen is a complex sugar that is stored in your muscles and liver.  This is the fuel that marathoners have in mind when “carb-loading” the week before the marathon.  They are topping off that supply to have as much energy as possible available on race day.  If you are eating well on a regular basis, you have a supply of energy.  How much?  A person weighing 150 lbs can carry anywhere from 800 to 2000 calories.  The more healthy carbs you eat, the more glycogen you are able to store.

Hydration is just as critical, if not more so.  A body without a full supply of water will not operate well.  The tougher your workout, the more water you will need.  Work on hydration on an ongoing basis throughout the day, starting with 16 ounces of water when you wake up!

My Personal Habit:

When I am training for a marathon, I will not eat 2-3 hours before one of my key workouts for the week.  I do, however, consume calories immediately before as well as throughout my run!  Specifically, I consume the fuel that I will consume during the marathon.  Since you absolutely must consume calories during a marathon, this method of consuming calories during my workout prepares my body to run fast while processing small amounts of easy-to-digest fuel.

When I am not in marathon training, I am more likely to just follow the 2 hour rule.  Since nearly all of my runs are shorter than 10 miles, I know my body stores enough glycogen to fuel any run – because I am eating right.  :)

AFTER any challenging run, I fuel up with high quality carbs and some protein as soon as I can.  This is the ideal time to replenish the glycogen supply and start healing those muscles.

Eat well & enjoy the run!

_____________

The Gift of Running,by P. Mark Taylor, is now available in both paperback & e-book

Paperback Version – Amazon.com $9.00

Ebook Version – Kindle Store $2.99

Ebook Version for Nook $2.99

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  1. For the longest time I would eat nothing prior to training, even before long runs, say a half-marathon or longer. I can still get away with up but it catches up to me around miles 17-18 so I’ve made it a point to incorporate eating something beforehand as part of my training. Last Saturday. Last Saturday I was in a hurry so I actually munched on a banana nut muffin over the first ten miles of my 19 miler.

  2. What’s your fuel of chocie Mark?

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