nificant amounts of plant foods were also consumed. These included
vegetables, fruits, nuts and seeds, which help protect against the
potential effects of high intakes of saturated fat. In addition, our ances-
tors were very active physically. Only in the last 5,000 years has this
changed. The Agricultural Revolution brought a dramatic increase in
carbohydrate foods, and the Industrial Revolution brought highly
refined carbohydrates to the table. The intake of carbohydrates by
humans has never been so dramatically high as it has been in just the
last 100 years. This relatively short period of significant dietary change
has contributed to many problems leading to heart disease, cancer,
obesity and other diseases.
For most people, eating such a high-carbohydrate diet can reduce
fat-burning and energy production, increase body-fat storage, signifi-
cantly reduce overall health, and greatly diminish human performance.
Carbohydrates and Insulin
Common foods including breads and other items made with flour
such as rolls, muffins, pancakes, waffles, cereals and pasta are among
the highest in carbohydrates. Also included in this category are all
sweets, including the hidden sugars found in many foods. One of the
main problems associated with eating carbohydrates has to do with
insulin.
Insulin is a hormone made by the pancreas. When you eat carbo-
hydrate foods, they are digested and the carbohydrate is absorbed
into the blood as glucose (blood sugar). This stimulates the release of
insulin, which has many different jobs. Three key actions of insulin on
blood sugar include the following:
- About 50 percent of the carbohydrate you eat is quickly
used for energy in the body’s cells. (Earlier we talked
about getting energy from both sugar and fat — this is
the part that comes from sugar.) - About 10 percent of the carbohydrate you eat is convert-
ed to and stored as glycogen, a reserved form of sugar.
When blood sugar is low, glycogen stored in the muscles
and liver is converted back to glucose and used for ener-
gy. (Muscle glycogen is used for energy by the muscles
30 • IN FITNESS AND IN HEALTH