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Health & Exercise Forum

Fueling Up for Exercise: Is it Better Before or After?

Mar 10, 2014

Dr. Mackarey's Health & Exercise ForumWhen is the optimal time to eat with regard to exercise? Will eating before exercise cause cramping? Will it negatively affect performance? Will eating after exercise make me nauseous or tired? These questions enter the minds of almost every amateur or competitive athlete engaged in exercise or sports.

Some people report upset stomach and cramping if they eat too soon before exercise; while others notice being tired and listless if they exercise without eating first. While the value of specific foods, quantity and timing of meals may vary with each individual with regard to sport and exercise, research supports the basic physiologic principle that active muscles need fuel. The fuel can be provided before or after exercise or both. The specific foods, timing and quantity of the meals must be individualized by self-experimentation.

Eating After Exercise

Several studies support the benefits of eating after aerobic exercise:

Promoting “Afterburn” – to continue burning calories 1-3 hours after exercise

Aerobic exercise at a moderate/maximal intensity for 30 to 45 minutes, raises the metabolic rate to a level that will continue burning calories for 1-3 hours following the activity, depending on the intensity, according to a study conducted at the Health Promotion and Wellness Center at the School of Medicine at University of Louisville in Kentucky.

Converting Carbohydrates to Glycogen – rather than fat

Eating after exercise fosters depletion of muscle glycogen stores, therefore, carbohydrates eaten after exercise are more efficiently converted to glycogen rather than stored as fat.

Suppress the Appetite – for 30 minutes following exercise

If the intensity of the aerobic exercise is great enough, it can suppress the appetite for half an hour following exercise. 30 minutes at maximum/moderate intensity was found to be more effective than 60-70 minutes at minimum intensity in suppressing the appetite. It is theorized that this may be due in part to an elevation of body temperature, which suppresses the appetite until the body cools down.

Eating Before Exercise

Due to schedule conflicts or preferences, some people may choose to exercise after a meal. One must be cautious, due to the fact that during vigorous exercise the digestive tract may receive only 20% of its normal blood flow. The hard working heart and muscles take priority. This slows digestion and may cause stomach distress. However, if the right kind of exercise is performed, it can prove beneficial. Minimal to moderate, not vigorous exercise is appropriate after a meal. This would include a brisk walk, low intensity cycling, gardening, or playing catch. Also, the right kind of food is important such as a moderate amount carbohydrate and protein will go a long way to provide fuel for exercise. For example, a plain bagel (carbohydrate) with peanut butter (protein) is the preferred fuel source for many athletes.

In conclusion, active people must experiment with food types, quantity and timing of meals with exercise for individual preference. However, if weight reduction is a goal, plan your meals within 1-2 hours following exercise at moderate/maximum intensity for 30 to 45 minutes. This strategy will enhance your chances of benefiting from the weight reduction value of exercise: the benefits of depleting calories 1-3 hours after exercise, more efficiently converting carbohydrates to glycogen rather than fat, and appetite suppression. However, if you require fuel for a prolonged activity, try a bagel with peanut butter.

Visit your doctor regularly and listen to your body.

NEXT MONDAY – Read Dr. Paul J. Mackarey “Health & Exercise Forum” in the Scranton Times-Tribune.

This article is not intended as a substitute for medical treatment. If you have questions related to your medical condition, please contact your family physician. For further inquires related to this topic email:

Paul J. Mackarey PT, DHSc, OCS is a Doctor in Health Sciences specializing in orthopaedic and sports physical therapy. Dr. Mackarey is in private practice and is an associate professor of clinical medicine at TCMC.