Nutritional bars are easily digested, help to manage blood sugar, etc.

Nutrition Bars come in many different varieties. An energy bar is a dietary supplement often consumed by athletes or other physically active people to maintain their calorific needs in light of their strenuous physical activity. As the name indicates, they are mainly a source of food energy, primarily complex carbohydrates. Some bars contain a source of protein (often whey, casein, or soy), as well as a selection of vitamins and minerals. The flavours added to the ingredients often make them resemble baked goods, such as cookies or muffins, to make them more appealing. The packaging of a typical bar will provide a precise nutritional breakdown in order to assist the athlete in maintaining a dietary regimen. Major brand names in North America include the Balance Bar, PowerBar, and Clif Bar. It is also possible to make one's own energy bars using an online recipe or a baking mix.

Energy bars provide a higher concentration of carbohydrates, along with proteins and fats, to give the body the fuel it needs to continue functioning. Most energy drinks on the other hand, offer a burst of intense energy followed by a crash. Their main mechanism of action is metabolic stimulation through B-complex vitamins and Central nervous system stimulation through caffeine (and in some cases more exotic "uppers" such as the yohimbine in Redline or ephedra in Stacker 2). Energy drinks thus enable the body to burn fuel faster than ordinarily possible, but once the fuel is burned up, the body effectively "runs out of gas" by crashing. Energy bars provide a massive amount of fuel for the body but do not induce metabolic stimulation to aid in the processing of that fuel.

Calories in food come from three main sources: fat, protein, and carbohydrates. In one gram of fat, there are nine calories; in one gram of protein or carbohydrates, there are four calories. Carbohydrates are a key ingredient in energy bars. There are two types of carbohydrates: "simple" carbohydrates, which are digested quickly by the body, and "complex" carbohydrates, which take longer to digest. However, this term is misleading. For example, starches, often labeled as complex carbohydrates, are essentially stored glucose and are actually digested more quickly than sucrose and fructose, so-called "simple" carbohydrates. Any form of digestible carbohydrate will eventually cause a spike in blood sugar. Fiber is often added to energy bars to add bulk without calories and slow the absorption of glucose. It should be noted that insoluble fiber, like that found in whole grain wheat, does not do this. Many companies have started using it in energy bars to give consumers the feeling of satiety.