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Energy Bars: An Athlete's Friend or Foe?

By Ana Cintado

Index - Click on a topic to read that section

I. What are "energy bars"?

II. Two main types of energy bars:

III. Different brands of energy bars:

IV. The basic idea behind energy bars: "Carbohydrate loading"

V. Contradictory evidence


I. What are "energy bars"?

Definition and Contents:

An energy bar is a convenient, fortified snack-food containing a blend of simple and complex carbohydrates, protein, fat, fiber, and vitamins and minerals. The primary source of protein in energy bars usually comes from milk and the fiber comes from grains and oats. Some bars also contain additional herbs, such as ginseng and guarana, "to help provide maximum energy" and to stimulate the central nervous system ( wn/sportsbars.html). Others include sodium and potassium phosphate to increase oxygen consumption capacity and to prevent lactic acid buildup in the muscles. The size of an energy bar varies with each brand and can range anywhere from one ounce to more than five ounces. The majority contain 100 to 300 calories and get most of these calories (at least 60 percent) from carbohydrates (Walsh 1997). The bars are usually easy to digest and come in a wide array of flavors and textures. They are advertised by most manufacturers as an "optimum energy fuel" and are used mainly as a way to replenish the body's energy stores as they are being depleted (

Who are they for? Where are they found?

Energy bars are most often associated with top athletes and endurance sports, such as bicycling and running. Recently, however, they have started to attract outdoor enthusiasts, participants of team sports, and casual exercisers (McEvoy 1994). They are becoming so popular that even overweight individuals are eating them as a low-fat meal substitute (Runner's World 1994). Today they can be found almost anywhere: in sporting good stores, pharmacies, health food shops, and even several department stores (Lobb 1995).

When do you eat them?

Energy bars can be consumed before an event to ensure sufficient levels of muscle and liver glycogen (stored carbohydrate), during an event to stabilize or maintain blood sugar levels, or after an event to replace expended nutrients and to maximize recovery. Some people also eat them as a snack or meal replacement throughout the day. Specific times and amounts obviously vary for each person (

II. Two main types of energy bars:

1. High-carbo group

Most energy bars are placed in this group because they are high in carbohydrates and low in proteins and fats. Producers of these bars argue that a high portion of carbohydrates provides "a superior source of fuel for endurance performance and that the fewer fat calories you ingest in a pre-workout, the better". Several examples include PowerBar, Gatorbar and VO sub 2 Max (Lobb 1995).

2. Balanced group

Other energy bars (such as PR Bar and CarboCrunch) contain a more balanced mix of nutrients that reflect the 40-30-30 diet philosophy. In these bars, only about 40 percent of the calories come from carbohydrates and the rest of the calories are divided equally between protein and fat ( Manufacturers of this type of bar claim that the equal proportion of food groups leads to greater fat-burning during exercise. According to this theory, burning more fat allows the body to save carbohydrate stores for that "final push" at the end of a long workout or race, when they are most needed. These manufacturers also believe that the body's ability to tap stored fats is inhibited when carbohydrate rations are too high and that, as a result, fatigue can occur much sooner (Lobb 1995).

Which type do most nutritionists recommend?

Nutritionists tend to favor the high-carbo group. Therefore, they promote consuming bars that would give an individual extra energy but not extra fat calories to digest ( According to nutritionist Nancy Clark, M.S., R.D., of SportsMedicine Brookline in Brookline, Massachusetts, "the ratio of a runner's entire diet should be 60 to 70 percent carbohydrates, 10 to 15 percent protein and 20 to 25 percent fat". In her view, this ratio is consistent with standard guidelines for both sports and health (Lobb 1995).

Do consumers agree?

In contrast to the recommendations of nutritionists, several highly-accomplished athletes have had more success with the balanced type of bar, including road-race elitist Anne Marie Lauck and five-time Ironman Triathlon winner Mark Allen. However, one study showed that runners do not pay attention as much to the overall percentage of carbohydrates in a bar, but to the actual composition of the carbohydrates. Nutritionist Alice Lindeman, Ph.D., R.D., suggests that the blend of carbohydrates should be equal. Fifty percent should be simple carbohydrates which are important for the beginning phase of exercise and are used at a more rapid rate. The other fifty percent should be complex carbohydrates because they are released slowly into the blood and can be used when stores begin to diminish (Lobb 1995). Several sources of simple carbohydrates include honey, fructose, and corn syrup. Complex carbohydrates are found in maltodextrin, glucose polymers, or unprocessed rice, oats or wheat flour. A perfect blend of these ingredients offers the body a dose of energy that acts quickly but that also lasts a long time (

III. Different brands of energy bars:

As the energy bar industry continues to expand, more and more brands are being introduced into the market. As a result, each brand must make a different claim to set it apart from its competitors. Listed below are several brands and some of their biggest claims.

1. Clif Bar

-"baked and not extruded"

-"uses all natural, unprocessed ingredients"

-"100% wheat and dairy free"

-"weather friendly integrity"


2. MLO Hardbody Energy Bars

-"high quality protein"

-"formulated with MCT's: more immediate source of energy and not as readily

stored as body fat"

-"more body fat is burned as energy"

-"spares muscle energy stores"


3. Infinity2 E.N.E.R.G.Y. Bars

-"no high glycemic sugar and no cholesterol"

-"enzymes to assist in assimilating nutrients"

-"converts fat to energy with no let down"


4. Edgebar

-"an ideal balance of carbohydrates"

-"loaded with vitamins and minerals"

-"contains antioxidants to neutralize free radicals"

-"does not contain: cholesterol, preservatives, added fats, sucrose or lactose,

trans fatty acids"


5. Pure Delight Energy Bars

-"nutrition in disguise"

-"stay within the recommended daily fat intakes"

-"added benefit of two of the most widely recognized and used herbs--ginseng

and gotu kola"

-"naturally sweet taste"


Which type of energy bar is most popular?

As the first energy bar ever created, PowerBar is by far the top choice among performance-oriented athletes such as runners, cyclists, and triathlon participants (Runner's World 1994).

Nutritional Content:

PowerBar contains approximately 14 grams of simple carbohydrates and 28 grams of complex carbohydrates. Other nutritional elements include high quality lactose-free milk protein, supplements of branch chain amino acids specifically utilized during exercise, and balanced amounts of electrolytes, trace minerals, and vitamins associated with energy metabolism. In addition, they are water-based and have no oils or added fats. Any caffeine found in these bars occurs naturally in its ingredients. They are available in six different flavors and they provide 230 kcals of food energy.

How do they work:

When eating a PowerBar, one should drink 8 to 16 ounces of water to help maintain hydration (although energy drinks, coffee or tea can also be used). This liquid also serves to form a "gel" in the stomach as it is absorbed by the oat bran of the bar. The formation of this gel is desirable because it eliminates the sloshing of foods and minimizes the irritation of the mucous lining of the stomach. This gel-like substance makes it easy for the body to digest and draw nutrients from because it is low in fat. It also makes the nutrients available for longer periods of time because it releases them more slowly into the blood stream.

After beginning exercise, the simple carbohydrates in the bar are used to replenish those depleted in the blood. Then, as exercise continues, the chemical chains of the complex carbohydrates are unraveled and released into the blood stream to aid the working muscles. Meanwhile, the vitamins, electrolytes, and trace minerals serve to replace the reserves of the body.

Claims made in advertisements:

PowerBar is designed specifically to maximize "all the nutritional factors that enhance optimum performance". It provides its user with lasting energy and prevents the highs and lows most often associated with candy and other sugary foods.

They are said to be a nutritional addition to the diet of a young child, they are used successfully by many diabetics, and they provide essential nutrients needed during pregnancy.



IV. The basic idea behind energy bars: "Carbohydrate loading"

What is the role of carbohydrates in exercise?

When individuals are engaged in exercise, both stored carbohydrate and fat is utilized as a primary source of energy. The body uses carbohydrates by breaking them down into glucose (or blood sugar). Glucose can then be converted into muscle glycogen (or the stored form of carbohydrates). These two components are used as fuel at the beginning of exercise (Contreras 1996).

The body can only store a certain amount of glycogen. Therefore, any excess carbohydrates consumed are deposited as fat. As exercise continues at a comfortable rate, adequate oxygen needed to burn this fat becomes available. Later, at the point of fatigue, the body returns to using carbohydrate from glycogen. Therefore, one's endurance capacity is influenced by the availability of this metabolic fuel. The level of glycogen available for storage is effected by the amount of carbohydrate in the diet and the amount of training that takes place prior to an event ( /sportn1.html).

What is carbohydrate loading?

A technique known as carbohydrate loading requires "the pushing of extra glycogen into muscle storage". It is one of the few dietary methods that can actually improve one's physical endurance almost immediately. Implementing this strategy involves resting prior to a race or event and eating as many carbohydrates as possible. Most nutritionists recommend engaging in this process the week before competition. In addition, they claim that it works best for events lasting 60 to 90 minutes or more and for highly trained athletes who have developed a greater glycogen capacity (Contreras 1996).

Benefits of carbohydrate loading before exercise:

"In a classic study conducted by Christensen and Hansen in 1939, the benefits of increasing carbohydrate intake for endurance exercise was clearly demonstrated. More specifically, the study successfully showed that loading on this nutrient several days prior to an event increased one's respiratory exchange ratio and made exercise time to fatigue longer. In contrast, consuming a low carbohydrate diet lead to a lower respiratory exchange rate and to the reduction of exercise time before fatigue was experienced. A number of subsequent studies have served to confirm this result and to demonstrate that pre-exercise muscle glycogen availability enhances endurance performance. This increase in performance has been shown to occur despite the fact that the rate of muscle glycogenolysis is accelerated as a result of increased muscle glycogen availability. A possible explanation of this phenomenon may be that "the expanded muscle glycogen reserve compensates for any increase in glycogen utilization". Another possible explanation could be that "the greater muscle glycogen break down enables the maintenance of higher outputs and enhanced exercise performance following glycogen loading" (Hargreaves 1996).

Benefits of carbohydrate ingestion during exercise:

Enhanced performance due to carbohydrate loading is demonstrated in the increase of exercise time to fatigue and in the ability to maintain or increase "power output" during an event. It is argued that endurance is enhanced because glucose levels of the blood are maintained and because carbohydrates are oxidized at a rapid rate while muscle glycogen levels are low. As a result, the net muscle glycogen utilization remains unaltered during prolonged exercise. However, a recent study contradicts this explanation by suggesting that it is the reduction of muscle glycogen utilization that contributes to the increase in endurance capacity (Hargreaves 1996).

V. Contradictory evidence

Carbohydrate loading

Increased exercise performance following muscle glycogen loading has not been observed in every study. For example, an article released last year in Outside suggests that carbohydrate loading can lead to hormonal changes that causes the storing of more fat, prevents the burning of that fat and restricts the flow of oxygenated blood to the muscles (Tilin 1996).

Energy Bars

Some researchers claim that, although energy bars enhance endurance performance, the chemicals in them could actually harm the body (Roy 1990). In addition, some nutritionists also argue that one can get similar effects from foods that are less expensive and that are just as convenient. Some examples include fruits, bagels, yogurt, cereal, dried fruit, fig bars, and crackers. One nutritionist even makes the argument that although elite athletes promote the promising effects of these bars, many times the enhanced performance they experience are due to the fact that they are "used to existing on zero calories" ( nutrinew/sportn2.html).


1. Contreras, V Wade. "Competition nutrition," American Fitness 14: Mar 1996.

2. Hargreaves, Mark. "Carbohydrates and exercise performance," Nutrition Reviews 54: Apr 1996.

3. Lobb, Welles. "You can take it with you," Runner's World 30: Jul 1995.

4. McEvoy, Christopher. "Mega-bites," Sporting Goods Business 27: Jul 1994.

5. "Power Play," Runner's World 29: Jun 1994.

6. Roy, Karen. "What's in there," Bicycling 31: May 1990.

7. Titlin, Andrew. "With a little more lard," Outside 21: Feb 1996.

8. Walsh, Julie. "Alternative energy sources," Women's Sports and Fitness 19: Jan/Feb 1997.



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