WebMD Medical Reference in
collaboration with Cleveland Clinic
What Is
Obesity?
Obesity is an excess proportion of total body fat. A person is
considered obese when his or her weight is 20%
or more above normal weight. The most common
measure of obesity is the
body mass index or BMI. A person is
considered overweight if his or her BMI is
between 25 and 29.9; a person is considered
obese if his or her BMI is over 30.
"Morbid obesity" means that a person is
either 50%-100% over normal weight, more than
100 pounds over normal weight, has a BMI of 40
or higher, or is sufficiently overweight to
severely interfere with health or normal
function.
What Causes Obesity?
Obesity occurs when a person consumes more
calories than he or she burns. For many people
this boils down to eating too much and
exercising too little. But there are other
factors that also play a role in obesity. These
may include:
- Age. As you get older,
your body's ability to metabolize food slows
down and you do not require as many calories
to maintain your weight. This is why people
note that they eat the same and do the same
activities as they did when they were 20
years old, but at age 40, gain weight.
- Gender. Women tend to
be more overweight than men. Men have a
higher resting metabolic rate (meaning they
burn more energy at rest) than women, so men
require more calories to maintain their body
weight. Additionally, when women become
postmenopausal, their metabolic rate
decreases. That is partly why many women
gain weight after menopause.
- Genetics. Obesity (and
thinness) tends to run in families. In a
study of adults who were adopted as
children, researchers found that
participating adult weights were closer to
their biological parents' weights than their
adoptive parents'. The environment provided
by the adoptive family apparently had less
influence on the development of obesity than
the person's genetic makeup. In fact, if
your biological mother is heavy as an adult,
there is approximately a 75% chance that you
will be heavy. If your biological mother is
thin, there is also a 75% chance that you
will be thin. Nevertheless, people who feel
that their genes have doomed them to a
lifetime of obesity should take heart. Many
people genetically predisposed to obesity do
not become obese or are able to lose weight
and keep it off.
- Environmental factors.
Although genes are an important factor in
many cases of obesity, a person's
environment also plays a significant role.
Environmental factors include lifestyle
behaviors such as what a person eats and how
active he or she is.
- Physical activity.
Active individuals require more calories
than less active ones to maintain their
weight. Additionally, physical activity
tends to decrease appetite in obese
individuals while increasing the body's
ability to preferentially metabolize fat as
an energy source. Much of the increase in
obesity in the last 20 years is thought to
have resulted from the decreased level of
daily physical activity.
- Psychological factors.
Psychological factors also influence eating
habits. Many people eat in response to
negative emotions such as boredom, sadness,
or anger. While most overweight people have
no more psychological disturbances than
people at their normal weight, about 30% of
people who seek treatment for serious weight
problems have difficulties with binge
eating. During a binge-eating episode,
people eat large amounts of food while
feeling they can't control how much they are
eating.
- Illness. Although not
as common as many believe, there are some
illnesses that can cause obesity. These
include hormone problems such as
hypothyroidism (poorly acting thyroid slows
metabolism), depression and some rare
diseases of the brain that can lead to
overeating.
- Medication. Certain
drugs, such as steroids and some
antidepressants, may cause excessive weight
gain.
Emotional Aspects of Obesity
One of the most painful aspects of obesity
may be the emotional suffering it causes.
American society places great emphasis on
physical appearance, often equating
attractiveness with slimness or muscularity. In
addition, many people wrongly stereotype obese
people as gluttonous, lazy, or both. However,
more and more evidence contradicts this
assumption. Obese people often face prejudice or
discrimination at work, at school, while looking
for a job, and in social situations. Feelings of
rejection, shame, or depression are common.
When to Seek Help
You should call your doctor if you are having
emotional problems related to your weight, need
help losing weight, or if you fall into either
of the following categories.
- If your
BMI is 30 or greater, you're considered
obese. You should talk to your doctor about
losing weight since you are at high risk of
having
health problems.
- If you have an "apple shape" - a
so-called, "potbelly" or "spare tire" -- you
carry more fat in and around your abdominal
organs. Fat in your abdomen increases your
risk of many of the serious conditions
associated with obesity. Women's waist
measurement should fall below 35 inches.
Men's should be less than 40 inches. If you
have a large waist circumference, talk to
your doctor about how you can lose weight.
Resource: Foxnews.com and WebMD, Edited by Cynthia Haynes, WebMD, October 2005.
Additional Resource:
DIET
FOR A PAIN-FREE LIFE, McIlwain, HH & Bruce, DF, Marlowe/Avalon, NY, in press,
December 2006