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Endurance athletes need low-glycemic foods to keep blood sugar levels steady, which is integral to sustaining energy and managing weight.

Whether you bike, hike, run, swim or cycle, blood sugar management is a key factor for endurance athletes, as important as having a regular training regime.  Just as your muscles need to be conditioned over time, your body needs to be fueled with the right nutrients to provide your muscles with the energy they need to perform at their optimum.

For endurance athletes to finish strong, they need to fuel up and address nutrition and hydration needs before and during activity to sustain blood sugars and energy levels.  Although most athletes are aware that carbohydrate foods provide energy before and during exercise, some are unaware of the differences between slow and quick-release carbs. The concept of carbohydrate foods, and their effect on blood sugar levels, can easily be explained.  

Move from low-carb to slow-carb

All carbs, including starches and sugars, are converted to glucose, which is blood sugar.  It is the rate at which your body converts carbs into glucose that is important. The answer is not to eliminate carbs but rather to manage them. Low glycemic foods help to keep blood sugar levels steady, which is integral to sustaining energy, managing weight and living vitally.  

Management of blood sugar levels involves many hormones, most importantly insulin. Here’s how it works: as a carb-containing food is eaten and digested, blood sugar rises and insulin is released to help your muscles use glucose for energy.  Excess glucose is stored as glycogen (in your muscles and liver) or fat (primarily in your liver). The key to sustained energy during endurance exercise is to eat foods that allow for a slow and steady conversion of glucose for energy. The slower the body converts glucose to energy, the better, as your “tank” stays fuller, longer.  

Choosing the right carbohydrates

Carbohydrates are the body’s preferred source of energy.  There are two main types of carbohydrates. Quick-release high glycemic index (GI) carbs spike blood sugar quickly, causing the body to release a flood of insulin to remove sugar from the blood.  This crashes the blood sugar level causing a craving for more food to bring the blood sugar level back up, leaving you feeling tired and lethargic.

Low glycemic index (GI) carbs, on the other hand, are recommended for endurance athletes as they take longer for your body to digest, allowing for a slow and steady release of glucose into the blood stream.  For steady blood sugar and long-lasting fuel for your muscles, substitute high GI snacks and energy bars (“kindling”) with low GI alternatives (“logs”).

Before exercise

Glycogen is the body’s storage form of carbohydrate. Fatigue and lowered performance can occur when muscle glycogen is used up.  “Consuming low GI foods before exercise may help to preserve muscle glycogen, saving this important energy source to fuel your muscles during the late stages of the ride or race,” explains Dr. Jonathan Little, Assistant Professor in the School of Health and Exercise Sciences at the University of British Columbia, Okanagan.

If you are partaking in an endurance activity within two hours of eating, keep snacks on the smaller side. One to two low GI certified SoLo GI Energy Bars in the 1-2 hours before exercise provides a great source of low glycemic nutrition for sustained energy.  Avoid snacks and granola bars that spike blood sugar, and low-carb bars filled with sugar alcohols or artificial sweeteners that may cause stomach upset and don’t provide sufficient energy.

During exercise

If your endurance activity lasts over 90 minutes, consume carbohydrates during your activity. This will spare glycogen stores and prevent blood sugar levels from dropping. Liquids (a sports drink) or solids are both effective.  Shoot for 30 – 75 g of carbohydrates per hour of activity or up to 90 g per hour if exercising for longer than 2.5 hours. The precise amount will depend on many factors, including individual tolerance, intensity and duration of exercise, hydration status, and environmental conditions.

Finally, when it comes to different foods, energy bars and drinks, use your training time to experiment so you can find what you like and what works best for your body. When you find what works well to keep your blood sugar and energy levels steady, stick with it to ensure you have the energy you need to finish strong.

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Saul Katz is a pioneer in the research and development of functional foods from natural ingredients that promote health, prevent disease and enhance performance. He is a founding Director of the Western Canadian Functional Food and Natural Health Product Network, and a past Director of the Alberta Food Processors Association. As CEO of SoLo GI Nutrition, he recently launched the first line of certified low glycemic and gluten-free SoLo GI® Energy Bars. (


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