Carbohydrates are utilized for energy, both
instant and sustained. When insufficient carbohydrates are taken
in, the body must utilize proteins for energy even to the point
of catabolizing muscle tissue for energy. The principle functions
of carbohydrates are to:
- Serve as the primary energy source for working muscles.
- Ensure that the brain and nervous system function properly.
- Help the body use fat more efficiently.
Digestive enzymes in the small intestines
break down the carbohydrates into glucose. The glucose can be
immediately utilized by the body or stored as glycogen in the
muscles and liver. The muscles can store about 20 minutes of
glycogen for energy. The bloodstream can hold about an hour
of glucose for energy.
If glucose levels are maximized and all glycogen
storage locations are full then the excess glucose is converted
to fat by the liver and stored in adipose tissue or fat cells.
There is really no limit to the amount of fat that a body can
store. According to studies at the University of Massachusetts,
carbohydrates are generally converted to fat at the rate of
75% where 25% of the carbohydrates are used in the conversion
Types of carbohydrates :
Monosaccharides are simple sugars and are
the basic unit of carbohydrate. Examples of monosaccharides
are glucose and fructose.
Disaccharides are composed of two monosaccharides.Examples
of disaccharides are table sugar (sucrose) which is composed
of fructose and glucose also milk sugar (lactose) which is composed
of glucose and galactose.
Polysaccharides are composed of multiple monosaccharides.
Examples of Polysaccharides are starches (bread, fruit, grain,
pasta, rice). These are also called complex carbohydrates.
Carbohydrates should comprise approximately
60% of the daily caloric intake. Therefore, for a 3000 calorie
total daily intake, 1800 of those calories should be carbohydrates.
Fiber is a form of carbohydrate. Approximately
20 grams of dietary fiber is required in our diets. Fiber facilitates
elimination and decreases appetite as a bulking agent. Fiber
also inhibits the absorption of cholesterol into the blood stream.
It has also been shown that fiber slows the absorption of sucrose
into the bloodstream.
This can be important in the treatment of
type II diabetes. Too much fiber in the diet can restrict the
absorption of necessary vitamins and minerals. Excess carbohydrates
are converted into fat by the liver and stored in adipose tissue.Sugar
is absorbed into the bloodstream within minutes. Consuming large
amounts of sugar prior to exercise can actually inhibit performance.
This produces a drastic increase in blood sugar.This causes
the pancreas to secrete large amounts of insulin to metabolize
All this insulin inhibits the metabolization
of fat by the muscles. Therefore, the muscles rely more on glycogen
which is in limited supply. The insulin reduces blood sugar
level which is already being reduced by the muscles utilization
of glycogen stores for energy production. The blood sugar level
reduces to a level which may not only cause fatigue but dizziness
as well. Therefore consumption of excess sugar prior to exercise
reduces performance and endurance.
Muscle glycogen depletion is a well recognized
limitation to endurance exercise that exceeds 90 minutes. Carbohydrate
loading can nearly double an individual's muscle glycogen stores.
Usually the loading has been preceded by a low-carbohydrate
diet, the only draw back may be hypoglycemia and ketosis, which
is associated by nausea, fatigue, dizziness and irritability.
It takes about 24 hours before muscle glycogen
is fully restored. When an individual is consuming carbohydrates,
relative to exercise, it is very important to refilling muscle
glycogen. By doing so within an hour or two, your muscle glycogen
storage and recovery is increased.