Carbohydrate consumption and exercise: Here's what you need to know

Low carb, complex carb or no carb - which one should you choose!?

The topic of carbohydrate consumption is highly debated when it comes to its role in the diet. Even more so when it comes to the needs and influences of carbohydrates in those who take part in regular exercise.

Some advocate cutting carbohydrates out completely, while others put them high up on the list of dietary needs. If you don’t know what you should be doing, this is for you…

But before getting into that, let’s look at what carbs are, first.


Not all carbs are created equal

Carbohydrates are one of the three macronutrients - including fats and proteins - that make up the foundation of every food we eat. Carbs are broken down into three main sugars - fructose, glucose and lactose - that the body can use as fuel, and also include starches and fiber.

Carbs are the main source of fuel for many bodily functions and play and important role in your health. They provide energy for the workings of the central nervous system and brain, they influence your mood and memory and are associated with higher dopamine levels1.

Eating carbohydrates also protects your body from using muscle protein as an energy source - which is, of course, something you want to keep when you’re training with a goal of building and strengthening your muscles2.

There are, however, different types of carbohydrates and not all are created equal.

In nature, both the forms of ‘complex carbohydrates’ and ‘simple carbohydrates’ occur. The difference between complex and simple is based upon the number of sugar molecules which are joined together to create that specific food.

Complex carbs are made of up a large number of sugar molecules and require extra energy to break down while being digested more slowly than simple carbs. Simple carbs, made up of two or less linked sugars, are quickly digested, providing fast energy spikes but, also, do not keep you full and will result in energy crashes. Simple carbs include foods such as white bread and white sugar.

It’s the complex carbs we want in our diets, which are found in whole fruit and vegetables, nuts and seeds, whole-grains, and legumes - for improving both physique and overall health.


To carb or not to carb?

To keep it simple, the amount of carbohydrates you decide to consume could depend on the type of exercise you’re doing.

In those who take part in endurance exercises, like long distance running, for example, a low to minimal carbohydrate diet may be more beneficial, in some cases3,4. This is because the energy needed to complete the exercise far outweighs the availability of carbohydrates and, so, the body switches to another source of fuel - namely fat and protein.

If the body is fed larger amounts of fat and is used to burning fat as a primary fuel source over carbs, such as is promoted by a ketogenic (high fat, low carb) diet, the fuel source for the endurance-type sport is immediately available and the body knows how to convert it to energy from the start.

That’s not to say that a higher carbohydrate, lower fat diet isn’t suitable for endurance athletes. In fact, some experts have argued that muscle cells prefer carbohydrates as their main fuel source5.

But, it does mean that those performing endurance activities will need a drastically higher amount of available carbohydrates to meet the energy requirements - such as is given during the practice of ‘carb loading’ before long races6.

If you don’t want to participate in a carb-loading style diet or are training to reduce body fat percentage, a higher fat diet, lower carbohydrate diet may therefore be a better overall option for endurance exercisers. On the other hand, if you’re training routine mainly consists of weight training and high intensity intervals, regular carbohydrate intake will be enough to meet these energy requirements without having to switch to fats or proteins as an alternate fuel source.

It can therefore be concluded that the choice to eat fewer carbohydrates, or to follow higher carbohydrate diet, can be guided by both the type of exercise that you take part in - and, of course, what feels best for your body and most sustainable for your mentality.

It’s important to remember that, whether you’re opting for higher or lower carbohydrate lifestyles, excluding carbohydrates is an extreme option that is not generally recommended.

Natural foods which are carbohydrate-rich, such as fruits and vegetables, provide many benefits like supporting gut bacterial balance, increasing fibre intake and bowel health, as well being rich nutrient sources to provide optimal training results and overall health7,8.

The exclusion of such foods can compromise digestive processes, bowel regularity, bacterial composition and make it more difficult to obtain optimal nutrient levels, which are of even greater importance to training bodies.

On a last note, it’s important to remember that each body is different.

Many people advocate at extreme ends of the carbohydrate spectrum - but, trust that when they do, it’s something they have found that works for them, and may not necessarily complement your personal biology.

Because each person is different, use carbohydrate recommendations that complement your training routine as general guidelines - but continue to pay attention to how your body feels in order to find the diet that works best for you as an individual.



  1. Kushwaha, P., et al. Bioactive carbohydrates. 2018. Secondary Metabolite and Functional Food Components: Role in Health and Disease. 197-222.
  2. Alghannam, A., et al. Influence of Post-Exercise Carbohydrate-Protein Ingestion on Muscle Glycogen Metabolism in Recovery and Subsequent Running Exercise. 2016.  International Journal of Sport Nutrition and Exercise Metabolism. 26(6):572-580.
  3. McSwiney, F and Doyle, L. Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism. 2018. 81:25-34.
  4. Maffetone, P., and Laursen, P. Reductions in training load and dietary carbohydrates help restore health and improve performance in an Ironman triathlete. Science & Coaching. 2017. 12(4):514-519.
  5. Phillippe, J., et al. Ketone Bodies and Exercise Performance: The Next Magic Bullet or Merely Hype? Sports Medicine. 2017. 47(3):383-391.
  6. Beelen, M., et al. Performance enhancement by carbohydrate intake during sport: effects of carbohydrates during and after high-intensity exercise. Nederlands Tijdschrift Voor Geneeskunde. 2015. 159:A7465.
  7. Knudsen, E. Microbial Degradation of Whole-Grain Complex Carbohydrates and Impact on Short-Chain Fatty Acids and Health. Advances in Nutrition. 2015. 6(2):206-213.
  8. Clemente, A., and Olias, R. Beneficial effects of legumes in gut health. Current Opinion in Food Science. 2017. 14:32-36.

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