What Causes Overweight and Obesity?
Energy Balance
For most people, overweight and obesity are caused
by not having energy balance. Weight is balanced by the amount of energy or
calories you get from food and drinks (this is called energy IN) equaling the
energy your body uses for things like breathing, digesting, and being
physically active (this is called energy OUT).
Energy balance means that your energy IN equals your
energy OUT. To maintain a healthy weight, your energy IN and OUT dont
have to balance exactly every day. Its the balance over time that helps
you maintain a healthy weight.
- The same amount of energy IN and energy OUT over
time = weight stays the same
- More IN than OUT over time = weight gain
- More OUT than IN over time = weight loss
Overweight and obesity happen over time when you
take in more calories than you use.
Other Causes
Physical Inactivity
Many Americans arent very physically active.
There are many reasons for this. One reason is that many people spend hours in
front of TVs and computers doing work, schoolwork, and leisure activities. In
fact, more than 2 hours a day of regular TV viewing time has been linked to
overweight and obesity.
Other reasons for not being active include: relying
on cars instead of walking to places, fewer physical demands at work or at home
because modern technology and conveniences reduce the need to burn calories,
and lack of physical education classes in schools for children.
People who are inactive are more likely to gain
weight because they dont burn up the calories that they take in from food
and drinks. An inactive lifestyle also raises your risk for
heart
disease,
high
blood pressure, diabetes, colon cancer, and other health problems.
Environment
Our environment doesnt always help with
healthy lifestyle habits; in fact, it encourages obesity. Some reasons
include:
- Lack of neighborhood sidewalks and safe places
for recreation. Not having area parks, trails, sidewalks, and affordable gyms
makes it hard for people to be physically active.
- Work schedules. People often say that they
dont have time to be physically active given the long hours at work and
the time spent commuting back and forth to work.
- Oversized food portions. Americans are surrounded
by huge food portions in restaurants, fast food places, gas stations, movie
theaters, supermarkets, and even home. Some of these meals and snacks can feed
two or more people. Eating large portions means too much energy IN. Over time,
this will cause weight gain if it isnt balanced with physical
activity.
- Lack of access to healthy foods. Some people
dont live in neighborhoods that have supermarkets that sell healthy foods
such as fresh fruits and vegetables. Or if they do, these items are often too
costly.
- Food advertising. Americans are surrounded by ads
from food companies. Often children are the targets of advertising for
high-calorie, high-fat snacks and sugary drinks. The goal of these ads is to
sway people to buy these high-calorie foods, and often they do.
Genes and Family History
Studies of identical twins who have been raised
apart show that genes have a strong influence on ones weight. Overweight
and obesity tend to run in families. Your chances of being overweight are
greater if one or both of your parents are overweight or obese. Your genes also
may affect the amount of fat you store in your body and where on your body you
carry the extra fat.
Because families also share food and physical
activity habits, there is a link between genes and the environment. Children
adopt the habits of their parents. So, a child with overweight parents who eat
high-calorie foods and are inactive will likely become overweight like the
parents. On the other hand, if a family adopts healthful food and physical
activity habits, the childs chance of being overweight or obese is
reduced.
Health Conditions
Sometimes hormone problems cause overweight and
obesity. These problems include:
- Underactive thyroid (also called hypothyroidism).
This is a condition in which the thyroid gland doesnt make enough thyroid
hormone. Lack of thyroid hormone will slow down your metabolism and cause
weight gain. Youll also feel tired and weak.
- Cushings syndrome. This is a condition in
which the bodys adrenal glands make too much of the hormone cortisol.
Cushings syndrome also can happen when people take high levels of
medicines such as prednisone for long periods of time. People with
Cushings syndrome gain weight, have upper-body obesity, a rounded face,
fat around the neck, and thin arms and legs.
- Polycystic ovarian syndrome (PCOS). This is a
condition that affects about 5 to 10 percent of women of childbearing age.
Women with PCOS often are obese, have excess hair growth, and have reproductive
and other health problems due to high levels of hormones called androgens.
Medicines
Certain medicines such as corticosteroids (for
example, prednisone), antidepressants (for example, Elavil®),
and medicines for seizures (for example, Neurontin®) may cause
you to gain weight. These medicines can slow the rate at which your body burns
calories, increase your appetite, or cause your body to hold on to extra
waterall of which can lead to weight gain.
Emotional Factors
Some people eat more than usual when they are bored,
angry, or stressed. Over time, overeating will lead to weight gain and may
cause overweight or obesity.
Smoking
Some people gain weight when they stop smoking. One
reason is that food often tastes and smells better. Another reason is because
nicotine raises the rate at which your body burns calories, so you burn fewer
calories when you stop smoking. However, smoking is a serious health risk, and
quitting is more important than possible weight gain.
Age
As you get older, you tend to lose muscle,
especially if youre less active. Muscle loss can slow down the rate at
which your body burns calories. If you dont reduce your calorie intake as
you get older, you may gain weight. Midlife weight gain in women is mainly due
to aging and lifestyle, but menopause also plays a role. Many women gain around
5 pounds during menopause and have more fat around the waist than they did
before.
Pregnancy
During pregnancy, women gain weight so that the baby
gets proper nourishment and develops normally. After giving birth, some women
find it hard to lose the weight. This may lead to overweight or obesity,
especially after a few pregnancies.
Lack of Sleep
Studies find that the less people sleep, the more
likely they are to be overweight or obese. People who report sleeping 5 hours a
night, for example, are much more likely to become obese compared to people who
sleep 78 hours a night.
People who sleep fewer hours also seem to prefer
eating foods that are higher in calories and carbohydrates, which can lead to
overeating, weight gain, and obesity over time. Hormones that are released
during sleep control appetite and the bodys use of energy. For example,
insulin controls the rise and fall of blood sugar levels during sleep. People
who dont get enough sleep have insulin and blood sugar levels that are
similar to those in people who are likely to have diabetes.
Also, people who dont get enough sleep on a
regular basis seem to have high levels of a hormone called ghrelin (which
causes hunger) and low levels of a hormone called leptin (which normally helps
to curb hunger). |