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I have read many articles in fitness magazines that have conflicting information about timing your meals with respect to exercising. Some say you shouldn't eat before, and some say you shouldn't eat right after exercising. What are the appropriate waiting times before and after? And also, does the timing change depending on whether you are doing aerobic or anaerobic training?


Great question! I'll address pre exercise, during exercise, and post exercise eating.

The short answer is a healthy diet will cover all the nutrition needs of regular exercise without any real special considerations. There are exceptions with sports competitions and workout sessions lasting longer than 2 hours.

Pre exercise: generally heavy meals immediately prior to exercise interfere with exercise through causing cramping or abdominal distress. The general rule is to consume your last full meal two hours prior to vigorous exercise or competition. If you are going to be exercising or competing for more than 1.5 to 2 hours, snacks like a banana or pure fruit juice (Rhino Fitness recommends Happy Planet Juice) before a workout are often beneficial because they supply muscles with energy (carbohydrates). For exercise lasting 90 minutes or less, there is no real need to take in energy immediately prior to or during exercise as the body stores more than enough carbohydrates for 90 minutes of activity.

During exercise: If your workout is 60 minutes or less it is unlikely you will require any replenishment during exercise if your food intake for the day is otherwise good. If exercise is longer than 90 minutes or 2 hours, you may need to replenish carbohydrates during the workout. It seems well accepted that a mix of about 6% sugar and water works well. Gatorade and PowerAde work, but so does splitting pure grape juice with 50% water. If using a premixed solution or your own mix, take in about 250ml (1 cup) of the carb/ water mix every 15 minutes.

You can also go old school and simply eat a banana or two during long workouts. Many runners and cyclists use "gel packs" a flavored sugary compound that is a little more thick than molasses sold in small palm sized foil packets. You must drink extra water when consuming gel packs; follow the recommendations on the label. It should be noted that conditioned athletes and exercise enthusiasts who are well conditioned typically don't need any carb replacment for training up to 2 hours in duration. If you know your 2 hour session is going to burn off more than 1500 calories, then a carb replacement should be considered.

Post workout: Perhaps the most important because recovery from your current workout is where preparation for your next workout begins. If your workout is 15 or 20 minutes there isn't any need for post exercise replenishment, because such a short workout is unlikely to deplete glycogen stores. For workouts lasting longer than 60 to 90 minutes, eating immediately after exercise can be vital if you are training or competing again in the same day or the next day. Exercise increases the efficiency at which you can load up your glycogen (carbohydrate) stores in your muscles.

There is a "glycogen window" that is wide open for about 20 minutes after you workout. After 20 minutes you begin reducing how effectively you can reload your muscles with glycogen and after about 60 to 90 minutes the window is effectively closed and you are back to normal glycogen storing ability. You need to eat the right amount of carbs and protein within this 20-minute window. The ratio is 4 to 1 carbs to protein. Both carbs and protein are absorbed better at this ratio post exercise.

Most brands of 1% chocolate milk are close to this ratio. Eating a banana will do, so will eating half a bagel. How much to take in? That is highly variable. It depends on how long and how hard you exercised and what quantity of carbohydrates you may have consumed during the workout, and how much you weigh. Typically it is not more than 150 calories for easy to moderate workouts and not more than 300 calories for intensive workouts. You would then eat a regular healthy meal within one hour. Post exercise nutrition can get more technical with eating smaller amounts at specific time intervals, but that is beyond the scope of the Ask The Coach format. Rhino Fitness can custom design specific pre/ during/ post nutrition intake for any person. If you miss your post exercise glycogen reload you can count on starting your next workout with sub-optimal energy stores.

Post exercise nutrition is important, but is over hyped by many, especially those selling post exercise nutrition products. Replenishing instantly after an aerobics class or spin class isn't necessary since caloric expenditure is likely to be less than 1000 calories. In this case, normal healthy eating will replenish your stores. Post exercise nutrition becomes critical for consecutive days of long intensive exercise or consecutive days of endurance sports competition.

Aerobic or anaerobic exercise doesn't change the guidelines I've suggested here for eating and exercise with the exception that many anaerobic workouts are shorter in total time and have more breaks within the workout body than steady state aerobic workouts and therefore some short but intensive workouts burn fewer total calories than a steady state aerobic workout done at the middle or high end of aerobic function. Shorter anaerobic workouts require less or most often no calories immediately post exercise - following a regular healthy diet will meet all the needs of short workouts.

If you are trying to lose fat and are reducing your caloric intake, post exercise eating (where necessary) is not the place to cut back. Reduce your calories at other times during the day. - Cris LaBossiere

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This page was last updated on August 6, 2007