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:
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IV. The basic
idea behind energy bars: "Carbohydrate loading"
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V. Contradictory
evidence
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REFERENCES |
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 (http://s2.com.etj/ 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 (http://s2.com/etj/wn/sportsbars.html).
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).
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 (http://s2.com/etj/wn/sportsbars.html).
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).
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 (http://s2.com/etj/wn/sportsbars.html).
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).
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 (http://s2.com/etj/wn/sportsbars.html).
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.
-"baked and not extruded"
-"uses all natural, unprocessed ingredients"
-"100% wheat and dairy free"
-"weather friendly integrity"
(http://www.lainet.com/pro/hpages/efoods/ClifBar.html)
-"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"
(http://www.adventuresports.com/asap/product/mlo/hardbod.html)
-"no high glycemic sugar and no cholesterol"
-"enzymes to assist in assimilating nutrients"
-"converts fat to energy with no let down"
(http://www.usasights.inter.net/nutranet/energybar.html)
-"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"
(http://www.haze.aust.com/asnc/edgebar.html)
-"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"
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.
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.
(http://www.powerbar.com/win/powerbar/nutri_fits.html)
(http://www.powerbar.com/lite/powerbar-faq.html)
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 (http://www.cheshire-med.com/services/dietary/nutrinew
/sportn1.html).
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).
"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).
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).
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).
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" (http://www.cheshire-med.com/services/dietary/
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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