Many types of energy bars are now available. From high-protein bars to those that are marketed specifically for women, the energy bar scene is anything but simple. Some label reading is a must when it comes to choosing the right bar for fueling. High-carbohydrate bars make great choices for carbohydrate fueling both before and during a long workout. These bars typically provide about 70 percent of their calories from carbohydrate as sugars (brown rise syrup, sucrose) and grains (oats and rice crisps).

Glycemic Index and Energy for a Workout

How quickly these carbohydrates get into the circulation is referred to as the glycemic index. Eating a high glycemic index bar means rapid release of carbohydrate into the blood stream, giving the muscles a quick “shot” of fuel, which is ideal during a workout. Eating a low glycemic index bar results in a slower release of sugar into the circulation and thus, sustained energy, which is best before exercise.

Many bar manufacturers claim that their profile of carbohydrates sources (such as oats and other complex carbohydrates) are best for a sustained and lasting release of carbohydrate fuel into the circulation. It’s true that carbohydrates are digested and appear in the circulation at different rates. Predicting the glycemic index of a bar based on it ingredients is challenging, as carbohydrate types digest at different rates and the protein and fat content of the bar also affect absorption. Most bars have high glycemic index despite their use of various grains and other complex carbohydrates as major ingredients.

What to Look For and How to Use

Select a bar with about 25-40 grams of carbohydrate and less than 15 grams of protein, which is not a crucial fuel source during exercise. Also, check the label for fat content as some bars can pack a hefty dose, which slows digestion and is not helpful during exercise or sports. Eat one bar about an hour prior to a long workout, and if you’re exercising for more than an hour eat one high-carb bar per hour of exercise along with ample water.

Source: “Selecting and Effectively Using Sports Drinks, Carbohydrate Gels, and Energy Bars,” by Liz Applegate, PhD, FACSM, and Kristine Clark, PhD, FACSM, ACSM. Reprinted with permission of the American College of Sports Medicine. Copyright © 2006 American College of Sports Medicine, www.acsm.org.