FUELIXIR’S FAST GUIDE TO THE GLYCEMIC INDEX


WHAT IS IT?

The glycemic index is a way of comparing different foods and their effect on the body’s blood glucose levels as compared to reference food (usually glucose or white bread). Pure glucose has a glycemic index of 100. Foods considered to be high on the glycemic index will have a score of >70, medium between 55 and 70, and low below 55. So, when you eat a meal or consume a drink that scores high on the glycemic index (for example some sugary cereal or soda) your blood glucose levels will rise higher and more rapidly than if you ate a meal that scored lower on the scale (for example bacon and eggs).


DON’T FORGET ABOUT THE LOAD

It’s not just the glycemic index you need to think about, arguably more important is the GLYCEMIC LOAD. Glycemic load of is calculated by multiplying the glycemic index of a food by the number of grams of carbs it contains, divided by 100. Why’s this important? Let’s look at an example. Both popcorn and watermelon are very high on the glycemic index with scores of around 72, but the glycemic load of these foods is very low, ~8 and ~4 respectively. So even though the glycemic index of these foods is high, you would need to eat a lot of them to elicit a significant blood glucose response. Spaghetti has a lower glycemic index, ~40, but its glycemic load is ~20. So eat too much pasta and your blood glucose will surge up.


AND THERE’S MORE TO IT…

The glycemic index of a food can actually change based on how you prepare the food. Eating something raw, like carrots, will elicit a different blood glucose response than if you were to steam or boil the food. Furthermore individual responses to foods can vary drastically. One person may respond with a large spike in blood sugar after eating a cup of white rice, whereas another person may respond completely differently with less of a blood glucose response. And get this, the blood glucose response an individual person has to a specific food can actually change based on WHEN the food is eaten (morning vs. evening for example).


WHAT’S THIS GOT TO DO WITH TRAINING AND RACING?

As you can see this gets complex, but here are just two easy takeaways that you can work into your endurance sport training and racing. (1) Just before exercise (<60 minutes) it may be a good idea to eat lower glycemic index foods. Research has suggested these foods to provide a performance benefit vs. higher glycemic index foods. (2) After exercise higher glycemic foods may be appropriate, especially after hard, intense, energy depleting efforts, to promote a more rapid recovery.


DROP THE MIC

It’s not just about the glycemic index. The glycemic load, the way in which the food is prepared, and the inner workings of the individual all factor in to how someone will respond to different foods.


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