What Athletes Need to Know About Sugar

August 18, 2016

People always ask me what the differences between type of sugars are, such as glucose, fructose, galactose, maltose, and lactose. It is important to understand the difference between them and utilize them at their best, as some will help your performance, while others may slow you down!

Sugars are a sub category of carbs. Many people do not know the difference between each type of sugar as they all provide the same 4 calories per gram and are absorbed using the same process. So what is the difference? Sugars differ in the way that your body utilizes them.

As an endurance athlete your body benefits from sugars more so than an unfit person as your body is more responsive to insulin (hormone that triggers uptake of glucose into cells) given your high amount of lean body mass. Given that your body utilizes sugars more efficiently, you will need less of this hormone to upload glucose.

During exercise, carbohydrates are the main source of energy and are mobilized throughout the body for contracting your muscles. As an athlete you need to optimize your carbohydrates stores before any exercise, all while maintaining the stores during a workout. During a workout, focus more on sugars and less on other types of carbohydrates (starches and fibres) as they are less likely to cause gut discomfort

Here is a table explaining the differences in metabolism of different types of sugars:

Fast absorption by the body

Slow absorption by the body


Fructose alone





Combined glucose and fructose





In your nutrition plan, include two sources of sugars during an exercise. Try to choose one fast and one slow absorbing sugar in order to avoid an energy crash (this happens when the sugar levels in your blood become low).

For example, if you consume fructose from a fruit, it will be absorbed slowly during your session causing symptoms like fatigue and cramps to arise quicker. On the other hand, if you have a source of glucose such as a gel containing only glucose, your body will feel a high, and then you will feel low energy afterwards.

So the secret is: Read the labels and find products that suit your needs!!

But the real question is still unanswered. How much sugar is a healthy amount to consumer in one day? According to Health Canada and the Dieticians of Canada, added sugars should be limited to 10% of your diet. Therefore, if you have a 3000 calories-diet, you should have no more than 300 calories of added sugars (3 energy gel packs). Thus, planning your nutrition plan with care is important.


Marina Parent

Dietitian-nutritionist, dtp.



Additional Reference

Wallis, Gareth A. "Roles of carbohydrates and sugars in sports nutrition." Canadian Sugar Institute. Birmingham: Canadian Sugar Institute, 01 January 2016. Electronic Document.

Photo Credit: Freepik

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