Sunday, August 3, 2008

Alternative Fuel Sources

Q: Hi Jonathan! I noticed a co-worker eating three pieces of fruit while dressed in sweats and holding a bottle of water. I quickly and correctly deduced that she had just been exercising and asked her about her choice of food. She said that her trainer told her to carb up both before AND after exercising (and to do it within half an hour after exercising). I thought you were supposed to have carbs first, then the protein?

What kind of foods should she eat both before and after, how soon, and if protein is involved, what kinds (cheese, milk, meat, fish, etc)? My co-worker is trying to lose weight and get in better shape. Thanks!

A: There is so much information, mis-information and different "rules" concerning nutrition, it's enough to make your head spin!

Although there is still a great deal of controversy concerning how much protein is really needed for muscle growth, the more practical and logical approach is that protein should be eaten throughout the day, and there really shouldn't be any meals that do not have a portion of protein in them. For instance, if you need 200 grams of protein per day and you eat 5 times a day, you should be shooting for roughly 40 grams of protein/meal.

While cheese is certainly a source of protein as you suggested, this may not be the best choice for a post-workout protein source because most cheeses are going to be higher in fat than protein, other than cottage cheese. However, given the high bioavailability of the milk proteins found in cheese (the measure of the how easily and efficiently the protein is delivered, or the ability of the body to digest and use the amino acids in the protein), a glass of milk or even chocolate milk can both be excellent choices for post-workout "meals."

There has been a great deal of interest in pre-workout nutrition in recent years, and a growing amount of evidence that supplementation with amino acids (the basic building blocks of protein) before your workouts can help to improve performance. Of course, coaches and athletes alike have known this for years, but it's nice that there is finally evidence to support the practice! In these studies, participants normally ingest a mixture of carbohydrates and proteins before engaging in exercise. Even if you choose not to follow the study methods exactly, a more "normal" meal of protein plus carbohydrates and healthy fats would still be a better choice for pre-workout "fuel" than simply ingesting carbs alone. There is also evidence that suggests that both carbohydrates as well as fats are effective at reducing protein catabolism which is a normal byproduct of exercising (and something that, if reduced, can improve muscle retention). Adding protein and/or fat to a carbohydrate-heavy meal improves blood-sugar response over longer time periods, which will allow for longer lasting energy levels.

Of course, it will also depend on goals: for an endurance athlete, more carbs and total calories throughout the day might be in order (For instance, Michael Phelps, a multiple Olympic gold-medal winner and multiple world-record holder in swimming, consumes over 10,000-12,000 calories per day during his heaviest training periods, with a huge portion of that coming in carbs. At 6'4", he's only 15-20 pounds heavier than I am, yet I eat somewhere around 1/3rd of his intake because the energy requirements of my workouts aren't even close to those of an Olympic swimmer!). On the other hand, for someone trying to lose weight and body fat, carbohydrates in the diet are best absorbed immediately after a strenuous workout because of exercise-induced changes in carbohydrate tolerance.

Timing, to some extent, is relative to the individual and the size of the meals. Some people have difficulty working out within an hour of eating and will feel nauseous from it, while others (like me) can eat something while walking through the gym doors without issue. In general, you should experiment with nutrient timing with your pre-workout meals to determine your individual best response. Depending on the form (liquid vs. whole foods) digestion can occur in a range of a 10-20 minutes to 2-3 hours. Usually 1-2 hours beforehand is a good place to start. As mentioned above, ingesting a protein + carbohydrate meal as soon as possible after your workout has repeatedly been shown to be the best strategy.

Of course, all of this is honestly only the tip of the nutritional iceberg! That's why when I have questions about nutrition, I turn to my friends Cassandra and Mike to sort through the food confusion and give me the best information available...I prefer biomechanics and exercise anyway!

-Jonathan

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