AHA
Scientific Position
Obesity
is defined simply as too much body fat.
Your body is made up of water, fat, protein, carbohydrate
and various vitamins and minerals. If you have too
much fat — especially in your waist
area — you're at higher risk for
health problems, including high blood pressure,
high blood cholesterol, diabetes, heart disease
and stroke.
Obesity
is now recognized as a major risk factor for coronary
heart disease, which can lead to heart attack.
Some reasons for this higher risk are known, but
others are not. For example, obesity
- raises
blood cholesterol and triglyceride levels.
- lowers
HDL "good" cholesterol. HDL cholesterol is linked
with lower heart disease and stroke risk, so
reducing it tends to raise the risk.
- raises
blood pressure levels.
- can induce
diabetes. In some people, diabetes makes these
other risk factors much worse. The danger of
heart attack is especially high for these people.
Even
when there are no adverse effects on the known risk
factors, obesity by itself increases risk of heart
disease. It also harms more than just the
heart and blood vessel system. It's a major cause
of gallstones and can worsen degenerative joint
disease.
Obesity
is mainly caused by taking in more calories than
are used up in physical activity and daily life.
When people eat too many calories, or too much saturated
fat, trans fat and cholesterol, their blood
cholesterol levels often rise. That raises their
risk of heart disease.
How
is body fat measured?
Waist
circumference measurement and body mass index (BMI)
are the recommended ways to estimate body fat. A
high-risk waistline is 35 inches or higher for women,
and 40 inches or higher for men.
The
body mass index formula assesses body weight relative
to height. It's a useful, indirect measure of body
composition, because in most people it correlates
highly with body fat. Weight in kilograms is divided
by height in meters squared (kg/m2). Or multiply
weight in pounds by 703, divide by height in inches,
then divide again by height in inches. In studies
by the National Center for Health Statistics,
- BMI values
less than 18.5 are considered underweight.
- BMI values
from 18.5 to 24.9 are normal.
- Overweight
is defined as a body mass index of 25.0 to less
than 30.0 (consistent with U.S. Dietary
Guidelines for Americans). A BMI of about 25
kg/m2 corresponds to about 10 percent over ideal
body weight.
- Obesity
is defined as a BMI of 30.0 or greater
(consistent with criteria of the World Health
Organization), or about 30 pounds or more overweight.
Extreme obesity is defined as a BMI of 40 or
greater.
See
"Body
Composition Tests" in this guide for more detailed
information and a BMI risk level table for adults.
Related
AHA publications:
Related
AHA Scientific Statements:
Obesity |
