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Paging Dr. Frischer - Exercise
WRITTEN BY :   Dr. Alan Frischer

Calling all exercise nuts…and everyone else who works out! (You can assign me to the “exercise nut” category.) What should we eat before we exercise, and what should we eat after? For those who exercise for extended periods, just how do we refuel during our workout?
Generally, in order to benefit the most from cardiovascular exercise (exercise that speeds up the heart and respiration), eat lightly about one hour before. This allows some time for digestion, and will provide the energy you need for your workout.
It is not generally true that eating immediately prior to exercise will give the muscles instant energy, because in order to provide nutrients and energy, food must be digested. The digestive process breaks food down into smaller compounds, yielding amino acids, fatty acids, and glucose. These nutrients are then transported to the body’s tissue through the circulatory system.
The problem is that during digestion, blood flow is shifted away from the brain and muscles and to the internal organs, for digestion and elimination. This shift in blood flow has a significant negative impact on the brain and muscle tissues, and lowers athletic performance.
What about consuming foods before exercise that require little or no digestion? These include fast-digesting carbohydrates and proteins. Fast-digesting carbs are highly processed foods such as white bread, white rice, mashed potatoes, cold cereals, fruit juices, foods with glucose (table sugar), fructose (fruit sugar), and the ever-present power/protein bars consumed by most serious athletes. Whey protein tends to be the fastest digesting protein, and is available in protein bars as well as in a powder form that is commonly added to shakes or other drinks.
Most athletes use these types of snacks for instant energy to the muscles. In fact, every marathon runner I know consumes them during the 26.2-mile race. However, recent studies reveal a major potential problem: Consuming either carbs or fast-releasing protein prior to or during exercise elevates plasma cortisol levels. Consistently elevated cortisol levels are associated with muscle wasting and fat gain! However, occasionally elevated cortisol levels during that occasional race are probably not going to pose a long-term health issue.
So, eating immediately before exercise tends to rob the brain and muscle of energy due to the digestive process, but when fast-releasing foods are consumed before exercise on a regular basis, the problem only becomes worse, due to elevated cortisol levels which may severely compromise ones ability to build muscle and burn fat. Do not make a habit of eating just before or during exercise.
Immediately after exercise, however, eating fast-releasing proteins and carbs is ideal. The ideal snack during the 30-60 minutes following your workout is light and nutritious, containing mainly carbohydrates and protein in a ratio of about 2:1. This might be one cup of fruit with protein powder, one cup of one percent milk, fat-free ice cream or nonfat yogurt, one apple with one-inch cube of low-fat cheese, or two slices of whole wheat bread with two thin slices of turkey or cheese.
Always make sure you are well hydrated before exercise. Exercise performance suffers with as little as two percent loss of body weight due to dehydration. Try to drink at least two cups of water two hours before the workout, and drink another two cups 20 minutes before.
For athletes entering a race or other competition where a bathroom stop just isn’t practical, drink lightly before the competition and replace fluids during. After your workout, drink more water than you feel like drinking; exercise actually blunts the sense of thirst. If you wait until you notice it, you’re already dehydrated. It’s a myth that drinking will cause an upset stomach or muscle cramps; in fact, muscle cramps are actually caused by water loss. Salt tablets will only aggravate the situation by drawing fluids into the stomach. The best way to prevent muscle cramps during exercise is by keeping well hydrated.
Did you know that almost all weight lost during exercise is due to water loss? (Sorry about that!) However, a long-term exercise program can certainly lead to weight loss.
For those who exercise up to an hour in moderate conditions, the most appropriate fluid is cool water. The typical American diet already contains adequate electrolytes (sodium, potassium, chloride, and magnesium) to replace what is lost by sweat. However, if you exercise for more than an hour in moderate conditions, or for less than an hour in extreme conditions, you may benefit from a sports beverage containing carbohydrates and electrolytes.
The ideal time for fitness activity is:
•1/2 hour after a light snack
•One hour after a light meal, heavy snack, or meal replacement drink
•Two hours after a regular meal
•Three hours after a Thanksgiving-type feast
•During an extended and vigorous sports event or race, but not on a regular basis.
I wish you healthy eating and exercising!
Dr. Alan Frischer is former chief of staff and current chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.

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Published: August 14, 2009 – Volume 8 – Issue 17



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