PT on the Net Research

Food Intake and Exercise


Question: 

What do you suggest telling clients about the timing of meals pre and post exercise session? I have seen conflicting research about exercising on an empty stomach versus eating a nourishing meal. I have also seen studies that say to eat within 10 minutes following exercise and others that say to wait 90 minutes. If the goal is maximizing fat burning, what do you suggest?

Answer:

If one has been fasting for more than three to four hours prior to his/her exercise session, then it would be ideal to consume a high carbohydrate snack prior to the session (10 to 15 minutes before): a snack containing 40 to 50 grams of CHO (i.e., Power Bar, banana plus raisins, half bagel with jam). The body will work more efficiently when blood glucose levels are normal. Plus, one needs to have glucose available in order for fat oxidation to take place.

If the exercise activity lasts more than 90 minutes, it is important to replace the CHO stores with a sports drink during the activity (i.e., six to eight ounces: half water/half Gatorade). A good rule of thumb is to consume one water bottle of fluids (12 to 16 ounces) per hour.

The first two hours post exercise would be the best time to replace the glycogen stores used during the activity. Approximately 0.75 grams of CHO per hour for every pound of body weight (i.e., female client at 140 pounds x 0.75 grams = 105 grams of carbohydrate). It is important to replace the CHO stores depleted during activity even if weight loss is the main goal. Keep in mind that one's metabolism will continue to be elevated for several hours post exercise.

As your client increases his/her cardiovascular endurance, fat oxidation will be enhanced. The more fit one is aerobically, the greater his/her fat oxidation during exercise. Also, one's metabolism will be higher for several hours following endurance activity. Keep in mind that duration and intensity of the activity plays a important role in fat oxidation (i.e., at least 45 to 60 minutes at approximately 60 to 70 percent of one's vo2 max).

Finally, it is the combination of physical activity (specially aerobic activity) and a decrease in total caloric intake that will best enhance weight loss. Nutrition and exercise go hand in hand.