Page 41 - 86 human physiology part-2

Chapter 13

therapy and if left untreated can cause death by ketoacidosis or dehydration shock. Type II also known
as non-insulin dependent diabetes ( NIDDM) appears usually after the age of 40 and accounts for the
majority of diabetes cases. The cause of NIDDM is usually a reduction in target cell responsiveness to
insulin.

Calories, Exercise, and Weight

Energy Balance and Body Weight

Energy is measured in units called calories. A calorie is the amount of energy that is needed to
raise the temperature of 1 gram of water by one degree Celsius. Because a calorie is such a small
amount, scientists use a larger unit to measure intake, called a kilocalorie. A kilocalorie is also referred
to often as a capital "C" Calorie, and is equal to 1000 calories. When we "count" calories, we are
actually counting the big Calories.

The old saying, "you are what you eat" is very much true. According to scientists, the average
adult consumes 900,000 calories per year. Most people tend to take in more calories than their body
needs. An intake of 12 extra calories a day, or around 5% excess in calories, yields an annual increase
of 12 extra pounds of body weight. The more developed countries tend to consume more calories than
others because of the increasing availability and dieting habits of eating refined foods with little
nutrition in them and lots of saturated fat. In our society, there is a huge emphasis put on a person's
image and how thin they are, and less emphasis put on what's most important--the nutrition our body
receives. While our body do need calories every day to keep us going, we need to watch the amount of
calories we consume in order to maintain good health and proper body weight.

Our Caloric intake is linked directly to our health status. Being overweight is generally defined as
being 15-20% above ideal body weight, while obesity is defined as being more than 20% above it.
People who weigh 10% less than ideal are considered underweight. This is less common in the more
developed countries. In less developed countries such as South Africa, being underweight is quite
common because they lack the nutrition to maintain good health.

How do we gain weight? When we consume more calories than our body can burn in a day, the
excess energy is stored in specialized cells as fat. It is also important to know that the three classes of
nutrients have different Caloric contents. Carbohydrates and proteins contain only four Calories per
gram, while fat contains about nine. Because of this, it is essential that we watch our amount of fat
intake. If we continuously feed our body more calories than is needed, our body will produce more fat
cells, to story the excess energy. This contributes to gaining weight.

It is more difficult for chronically overweight persons to lose weight than normal-weight persons.
This is because they are constantly fighting the body's own weight-control system, which responds as if
the excess weight were normal. Our body is capable of measuring how much we intake, and
maintaining our weight. When an overweight person goes on a diet, and consumes less calories, their
body will respond as if they are starving, and try to save energy where it can to make up for the
decrease in received calories.

Maintaining a healthy body weight

256 | Human Physiology