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Fueling Up During Exercise

You’ve fueled the tanks, and you are going the distance!  Suddenly, you begin to feel tired and uninterested before you’re even finished.  Those glycogen stores may be on empty, telling you it’s time to hit the pit stop before coming to a screeching halt.

Although this article may not be for all, the most avid exercisers may benefit from these essential eating strategies during an exercise session.  

As before, it’s important to understand the three W’s of fueling: Why, What and When.


During Exercise Fuel: Why?

After around 90 minutes of exercise, glycogen reserves are usually tapped out; the most accessible energy gets used up.  At this point, your body has switched to using more intramuscular fat and fatty acids, which are secondary sources of energy.  Unfortunately, the body slows down because the process of metabolizing fat for energy is not as efficient, requiring more metabolic steps at the cellular level.  You can avoid this.  Using exogenous, or outside sources of the simplest carbohydrate for fuel can keep the blood sugar high and provide those muscles and mitochondria exactly what they are looking for. 


During Exercise Fuel: What?

Simple fuel is a simple concept: sugar is best, with a little twist.

The simple sugars are already broken down, ready to be picked up and shuttled to the muscle and brain.

Sports drinks and gels like Gatorade and Gu gel are ideal.  They have one or two forms of simple sugar like glucose and fructose to ensure ample absorption through the gut wall and into the blood.  Each type of sugar requires a different receptor to get them through the gut wall and into the blood.  Receptors can be thought of as shuttle busses.  Utilizing both receptors, or shuttle busses, makes the process of fueling more efficient, and avoids a ‘long lines’ to take the shuttle through the wall and into your muscle. 

The sports drinks and gels also contain electrolytes, like sodium and potassium and magnesium.  These electrolytes act like ‘electricity’ to enable those muscular contractions to occur.  They work alongside those fueling sugars and fats.  Other good examples of quick energy are pretzels, fig newtons, small low fat crackers or cookies and candies like skittles and M and M’s and Coca Cola.  Usually foods you want to avoid, these are ideal for during the workout because they will be used efficiently for fuel.


During Exercise Fuel: When?

In this case it’s slightly obvious. The best time for consumption is during the workout, but only the longer ones!

30 to 60 grams of carbs is great during each hour of exercise over 1 hour.  Make sure it’s familiar food or drink with simple carbs, no fat and no fiber.  And spread it out!  Think of the calories and carbs that you are ingesting as a continuous IV drip, steadily washing through your blood and coating your working muscles with powerful propellant [i].

Experiment, and over time the fueling process will be second nature, and your exercise, a consistent daily activity.

Arguably the most important aspect of the exercise fueling window is the recovery period: that time when your muscles and fuel reserves are screaming for replenishment. 

[i] Coleman, E. (2011). Diet, Exercise, and Fitness, 8th Ed. Chapter 4: Fueling before, during and after exercise. Page 49-60
Jessica Iannotta, MS, RD, CSO, CDN

Jessica is a registered dietitian and certified specialist in oncology nutrition (CSO). She studied nutrition at Cornell University and completed her dietetic internship at New York Presbyterian Weill Cornell Medical Center. She obtained her Master's degree through the University of Medicine and Dentistry of New Jersey. Jessica has worked in inpatient and outpatient oncology settings since 2001 in the North Shore-LIJ Health System. Jessica is in charge of all operations including clinical and culinary operations ranging from menu development to evidence-based website content, relationships with registered dietitians and social workers and developing processes and protocols for intake, management and outcomes analysis of patients.

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