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More than 60
percent of Americans aged 20 years and older are
overweight. One-quarter of American adults are also
obese, putting them at increased health risk for
chronic diseases such as heart disease, type 2
diabetes, high blood pressure, stroke, and some
forms of cancer.
This fact sheet
provides basic information about obesity: What is
it? How is it measured? What causes it? What are
the health risks? What can you do about
it?
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| What is
obesity? |
To most people,
the term "obesity" means to be very overweight.
Health professionals define "overweight" as an
excess amount of body weight that includes muscle,
bone, fat, and water. "Obesity" specifically refers
to an excess amount of body fat. Some people, such
as bodybuilders or other athletes with a lot of
muscle, can be overweight without being
obese.
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| How is obesity
measured? |
Everyone needs a certain
amount of body fat for stored energy, heat
insulation, shock absorption, and other
functions. As a rule, women have more body fat
than men. Most health care providers agree that
men with more than 25 percent body fat and women
with more than 30 percent body fat are
obese.
Measuring the exact amount of
a person's body fat is not easy. The most
accurate measures are to weigh a person
underwater or to use an X-ray test called Dual
Energy X-ray Absorptiometry (DEXA). These methods
are not practical for the average person, and are
done only in research centers with special
equipment.
There are simpler methods to
estimate body fat. One is to measure the
thickness of the layer of fat just under the skin
in several parts of the body. Another involves
sending a harmless amount of electricity through
a person's body. Both methods are used at health
clubs and commercial weight loss programs.
Results from these methods, however, can be
inaccurate if done by an inexperienced person or
on someone with severe obesity.
Because measuring a person's
body fat is difficult, health care providers
often rely on other means to diagnose obesity.
Weight-for-height tables, which have been used
for decades, usually have a range of acceptable
weights for a person of a given height. One
problem with these tables is that there are many
versions, all with different weight ranges.
Another problem is that they do not distinguish
between excess fat and muscle. A very muscular
person may appear obese, according to the tables,
when he or she is not.
In recent years, body mass
index (BMI) has become the medical standard used
to measure overweight and obesity.
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Body Mass Index
|
BMI uses a
mathematical formula based on a person's height and
weight. BMI equals weight in kilograms divided by
height in meters squared (BMI = kg/m2). The BMI
table that follows has already calculated this
information.
Although the BMI
ranges shown in the table are not exact ranges of
healthy and unhealthy weight, they are useful
guidelines. A BMI of 25 to 29.9 indicates a person
is overweight. A person with a BMI of 30 or higher
is considered obese.
Like the
weight-to-height table, BMI does not show the
difference between excess fat and muscle. BMI,
however, is closely associated with measures of
body fat. It also predicts the development of
health problems related to excess weight. For these
reasons, BMI is widely used by health care
providers.
Find your weight on
the bottom of the graph. Go straight up from that
point until you come to the line that matches your
height. Then look to find your weight
group.
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Body Fat
Distribution: "Pears" vs.
"Apples"
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Health care providers are
concerned not only with how much fat a person
has, but also where the fat is located on the
body. Women typically collect fat in their hips
and buttocks, giving them a "pear" shape. Men
usually build up fat around their bellies, giving
them more of an "apple" shape. Of course some men
are pear-shaped and some women become
apple-shaped, especially after menopause. If you
carry fat mainly around your waist, you are more
likely to develop obesity-related health
problems. Women with a waist measurement of more
than 35 inches or men with a waist measurement of
more than 40 inches have a higher health risk
because of their fat distribution.
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| Causes of
Obesity |
In scientific terms,
obesity occurs when a person consumes more calories
than he or she burns. What causes this imbalance
between calories in and calories out may differ
from one person to another. Genetic, environmental,
psychological, and other factors may all play a
part.
Genetic factors
Obesity tends to
run in families, suggesting a genetic cause. Yet
families also share diet and lifestyle habits that
may contribute to obesity. Separating these from
genetic factors is often difficult. Even so,
science shows that heredity is linked to
obesity.
In one study,
adults who were adopted as children were found to
have weights closer to their biological parents
than to their adoptive parents. In this case, the
person's genetic makeup had more influence on the
development of obesity than the environment in the
adoptive family home.
Environmental
factors
Genes do not destine people to
a lifetime of obesity, however. Environment also
strongly influences obesity. This includes
lifestyle behaviors such as what a person eats and
his or her level of physical activity. Americans
tend to eat high-fat foods, and put taste and
convenience ahead of nutrition. Also, most
Americans do not get enough physical
activity.
Although you cannot change your
genetic makeup, you can change your eating habits
and levels of activity. Try these techniques that
have helped some people lose weight and keep it
off:
- Learn how to choose more
nutritious meals that are lower in
fat.
- Learn to recognize and
control environmental cues (like inviting smells)
that make you want to eat when you're not
hungry.
- Become more physically
active.
- Keep records of your food
intake and physical activity.
Psychological
factors
Psychological
factors may also influence eating habits. Many
people eat in response to negative emotions such as
boredom, sadness, or anger.
Most overweight
people have no more psychological problems than
people of average weight. Still, up to 10 percent
of people who are mildly obese and try to lose
weight on their own or through commercial weight
loss programs have binge eating disorder. This
disorder is even more common in people who are
severely obese.
During a binge
eating episode, people eat large amounts of food
and feel that they cannot control how much they are
eating. Those with the most severe binge eating
problems are also likely to have symptoms of
depression and low self-esteem. These people may
have more difficulty losing weight and keeping it
off than people without binge eating
problems.
If you are upset
by binge eating behavior and think you might have
binge eating disorder, seek help from a health
professional such as a psychiatrist, psychologist,
or clinical social worker.
Other causes of
obesity
Some illnesses can lead to obesity or a tendency
to gain weight. These include hypothyroidism,
Cushing's syndrome, depression, and certain
neurological problems that can lead to overeating.
Also, drugs such as steroids and some
antidepressants may cause weight gain. A doctor can
tell whether there are underlying medical
conditions that are causing weight gain or making
weight loss difficult.
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| Consequences
of Obesity |
Health
Risks
Obesity is more
than a cosmetic problem; it is a health hazard.
Approximately 280,000 adult deaths in the United
States each year are related to obesity. Several
serious medical conditions have been linked to
obesity, including type 2 diabetes, heart disease,
high blood pressure, and stroke. Obesity is also
linked to higher rates of certain types of cancer.
Obese men are more likely than non-obese men to die
from cancer of the colon, rectum, or prostate.
Obese women are more likely than non-obese women to
die from cancer of the gallbladder, breast, uterus,
cervix, or ovaries.
Other diseases and
health problems linked to obesity
include:
- Gallbladder disease and
gallstones.
- Liver disease.
- Osteoarthritis, a disease
in which the joints deteriorate. This is
possibly the result of excess weight on the
joints.
- Gout, another disease
affecting the joints.
- Pulmonary (breathing)
problems, including sleep apnea in which a
person can stop breathing for a short time
during sleep.
- Reproductive problems in
women, including menstrual irregularities and
infertility.
Health care
providers generally agree that the more obese a
person is, the more likely he or she is to develop
health problems.
Psychological and social
effects
Emotional
suffering may be one of the most painful parts of
obesity. American society emphasizes physical
appearance and often equates attractiveness with
slimness, especially for women. Such messages make
overweight people feel unattractive.
Many people think
that obese individuals are gluttonous, lazy, or
both, even though this is not true. As a result,
obese people often face prejudice or discrimination
in the job market, at school, and in social
situations. Feelings of rejection, shame, or
depression are common.
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| Who should lose
weight? |
Health care
providers generally agree that people who have a
BMI of 30 or more can improve their health through
weight loss. This is especially true for people who
are severely obese.
Preventing
additional weight gain is recommended if you have a
BMI between 25 and 29.9, unless you have other risk
factors. Obesity experts recommend you try to lose
weight if you have two or more of the
following:
- Family history of
certain chronic diseases.
If you have close
relatives who have had heart disease or
diabetes, you are more likely to develop these
problems if you are obese.
- Pre-existing
medical conditions. High blood pressure, high cholesterol
levels, or high blood sugar levels are all
warning signs of some obesity-associated
diseases.
- "Apple"
shape. If your
weight is concentrated around your waist, you
may have a higher risk of heart disease,
diabetes, or cancer than people of the same
weight who have a "pear" shape.
Fortunately, a
weight loss of 5 to 10 percent can do much to
improve health by lowering blood pressure and
cholesterol levels. In addition, recent research
has shown that a 5- to 7-percent weight loss can
prevent type 2 diabetes in people at high risk for
the disease.
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How is obesity
treated?
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The method of
treatment depends on your level of obesity, overall
health condition, and motivation to lose weight.
Treatment may include a combination of diet,
exercise, behavior modification, and sometimes
weight-loss drugs. In some cases of severe obesity,
gastrointestinal surgery may be recommended.
Remember, weight control is a life-long
effort.
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