Nutrition & Exercise Part 3: Nutrition While Exercising

nutrition during exercise

Fight your fatigue with carbs and fluids!

Imagine this: you are in the middle of a marathon – let’s say it the Flying Pig in downtown Cincinnati. You are at mile 14 and you are starting to feel fatigued. All of the nice people of Cincinnati are coming outside in their front yards and cheering you on. Kids are ringing cow bells, everyone is sitting in their lawn chairs, leisurely clapping as you run by. Suddenly, you wish you had a lawn chair. Hell, you are so tired you would just like to lay down on the pavement. There are fluid stations with paper cups filled with water, Gatorade and lemonade. You see people handing out Twizzlers, orange slices, and sports gels. You start thinking to yourself, “Do I stop and grab something?”

The answer is, YES!

Nutrition during long rounds of exercise is definitely important if you want to keep going. The 2 main focus points for today’s post: Carbohydrates and fluids.

Why carbohydrates?

Remember in Part 1 we talked about aerobic exercise? Aerobic activity uses glucose (sugar – the simplest form of carbohydrates) and stored glucose (glycogen) as it’s main energy source. Once your body detects that it is running low on glycogen stores, glycogen sparing takes into effect.

Glycogen sparing is just what it sounds – your body wants to spare the stored sugar and save it so it will then start using fat cells as it’s main energy source (yes! burn that fat!) Once the fatigue sets in, it’s important to grab those carbohydrates to help give your body the energy it needs to keep going.

Also, consuming carbs during long periods of exercise is important to prevent hypoglycemia – or low blood sugar. If you start feeling dizzy or like you are going to faint, grab a carb to bring that blood sugar back up!

Consuming carbs during a workout is especially important if you have been fasting. When a marathon starts at 6 am, make sure you give yourself time in the morning to get a good pre-exercise nutrition meal. If you don’t have time and you are working out for a long period of time, pack a carbohydrate snack to eat during your workout.

Carbohydrate Guidelines:

There was a study published in the Journal of Sports Science that was completely dedicated to carbohydrate consumption and athletes. Their findings are super interesting – here is a breakdown:

  • During brief exercise (lasting less than 45 minutes), carbohydrates are not generally needed during the workout
  • During a high-intensity exercise, lasting more than 45 minutes, less than 75 – small amount of carbohydrates are recommended (think: sports drink, sports gel, fruit)
  • Exercise lasting 1-2.5 hours, such as a soccer game, its recommended that you get about 30-60 grams of carbs per hour
  • Exercise lasting more than 2.5-3 hours – it’s recommended to have up to 90 grams per hour – that’s a lot!
  • According to the same study, higher intakes of carbs is associated with better performance

Carbohydrate Sources

So now that we know the importance of nutrition during exercise, let’s talk examples:

  • Sports drinks that contain carbohydrate and electrolytes
  • Easily digested carbohydrate-rich foods during endurance events, for example, banana, bread or roll with jam or honey, sports foods (gels, gummy chews), or bite-sized pieces of low-fat granola or sports bars
  • Fluids consumed with carbohydrate gels or carbohydrate-rich foods to speed fuel transport to muscles.


Before I end this post I do want to do a quick overview of fluids and talk about sweat rates. I will have a whole post dedicated to fluid intake and exercise, but let’s just get a little head start now while we are talking about nutrition during a workout.

Sweat is inevitable when you are working out. Fluids are most definitely lost with perspiration, so it is important to know that you need to replace them. But how do you know how much water you should drink to replace all of the lost sweat? Introducing the Sweat Rate Equation:

sweat rate

Find the difference in your weight (pre-exercise weight minus post-exercise weight) and add it to the amount of fluids you consumed during your workout. It’s important to note that this should be done in ounces (there are 16 ounces in a pound). Then divide that number by how long you exercised (30 minutes = .5 hours, etc)

The number you end up with is how much water you should consume during that particular workout to make sure you don’t experience dehydration. Don’t worry if you can’t replace it all – just remember this: Dehydration is considered a >2% weight loss difference. If you lose more than 2% of your pre-exercise weight during a workout, you are at risk for dehydration – so drink up!

Consumption of beverages containing electrolytes and carbohydrates can help sustain fluid and electrolyte balance and increase endurance exercise performance. Fluids containing sodium and potassium help replace sweat electrolyte losses.

More on fluid consumption to come 🙂