Eating before exercise: The facts

June 11, 1999
Web posted at: 11:27 AM EDT (1527 GMT)

In this story: Sometimes it could be dangerous For weight loss RELATEDS

By Miriam E. Nelson, Ph.D.

(WebMD) -- Many people have heard that you shouldn't eat before engaging in vigorous exercise. Is it okay to eat right before a strength-training session or a run? Will eating before a workout affect your progress if you're interested in weight loss?

After a meal, significant blood flow is directed toward the stomach to facilitate the digestive process. If you attempt to exercise soon after eating -- whether running or strength training -- blood flow must be redirected to working muscles. Therefore, the digestive process is compromised and many people may experience cramping in the abdominal area. Abdominal cramping after eating tends to happen more often with cardiovascular exercise than with strength training, although the process is the same with both.

Sometimes it could be dangerous

Some people feel sluggish if they have just eaten a big meal; running or other cardiovascular activities would inevitably be more difficult. There are some activities, such as swimming or rock climbing, where severe cramping could actually be dangerous, compromising your ability to execute a maneuver or the continuation of one. Therefore you should always allow adequate time for digestion -- at least an hour after finishing a meal -- before participating in these activities.

On the other hand, exercising on an empty stomach can also be difficult for some people, as they feel drained or out of energy. The ideal time to exercise would be approximately one-to-four hours after a meal. Exercising during this time allows the digestive system to complete its work, while you have eaten recently enough to avoid feelings of hunger. Remember, though, that it is important to stay hydrated before, during and after an exercise session.

For weight loss

If weight loss is a goal, it is most advantageous to eat after exercising. The reason is that if you have not eaten recently, you are most likely to utilize stored energy during the exercise session rather than the food you just consumed.

Copyright 1999 by WebMD, Inc. All rights reserved.

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