|
For
a Body Fat Tip Off, Look to Your BMI
A measure called body mass index may be a better gauge of
health than absolute body weight. You can calculate your
BMI
here
Overweight is associated with type 2 diabetes, heart disease,
certain forms of cancer and joint problems like osteoarthritis.
It is also clear that even modest weight loss can have profound
effects on health.
But it may take more than a mirror or an arbitrary "goal
weight" to get on the road to reducing health risk.
A body of research has found that body mass index, or BMI
may be a better indicator of health risk than absolute body
weight. In addition, where you gain the weight may be equally
important in determining your risk for certain diseases.
Though it is only one of a number of considerations that
health experts use to determine these risks, BMI is more
highly correlated with body fat that any other measurement
of height and weight.
Below, Anne Wolf, obesity expert and instructor of research
at the University of Virginia School of Medicine, offers
simple instructions for determining body mass index, and
talks about the usefulness of BMI in assessing health risk
and as a goal for weight loss.
What is body mass index, or BMI, and what does it measure?
Body mass index uses a person's height and weight to assess
that person's risk of health problems.
How is measuring BMI different from just asking someone
to step on a scale?
Weight alone is not a very good measure of body fat. BMI
is highly correlated with body fat, and, subsequently, health
risk.
Is BMI a new way to assess a person's health risk?
We used to assess a person's "ideal" weight using
height measurements, but we realized that it was sending
a very bad message. It implied that each person has an ideal
weight for their height, which is not true. In fact, there
is a range. It is more useful to understand that there is
a range where your risk for developing disease is minimized.
BMI is based on health risk, not on how you look.
How is BMI calculated?
The formula is a little complicated. The first step would
be to multiply your weight in pounds by 703. Next, multiply
your height in inches by your height in inches again. So
if you are 65 inches tall, you're going to multiply 65 by
65. The third and last step is to divide your answer in
step one-the weight by 703-by your answer in step two. That
will give you your body mass index. For instance, if you
are 124 pounds and 5 feet tall, your BMI would be 24.2.
And what is considered a healthy, and an unhealthy BMI?
A BMI of less than 18.5 would be underweight. A BMI between
18.5 and 24.9 would be considered a healthy body weight,
overweight is categorized as 25 to 29.9, and obesity is
categorized as a BMI of 30 and above.
Does BMI account for body proportion?
No. And in fact, one of the other measurements that the
National Heart, Lung and Blood Institute recommends using
with body mass index to assess health risk is waist circumference.
We know that a high waist circumference-or high amounts
of abdominal body fat-is very dangerous body fat to have,
independent of a high body mass index.
So if someone has a body mass index in a healthy range
but they have a very high waist circumference, then they
still are at risk of developing disease states.
What sorts of health risks does a high BMI pose?
People with high BMI are at very high risk of developing
type 2 diabetes and cardiovascular disease. That includes
coronary heart disease, hypertension, stroke, and enlarged
heart. It's also involved very much with the whole metabolic
syndrome. You're at a higher risk for insulin resistance,
infertility, and polycystic ovary syndrome. You're at high
risk for certain types of cancers, and particularly cancers
of the reproductive system-endometrial cancer, breast cancer,
etc. Colon cancer for men. We've seen associations with
gall bladder cancer, as well, and some other smaller types
of cancer.
A high BMI is also associated with structural problems.
A lot of people who have a body mass index over 30, which
is very high, have many more hip and knee problems, osteoarthritis,
and also problems in the hand.
So the health risks are pervasive. They're not just diabetes
or heart disease. It also hits the structural system and
is highly associated with cancers, and lower quality of
life.
Is BMI genetic?
If your family is heavy, you are more likely-for genetic
reasons-to be more heavy set than other people. However,
genes don't change, and in the last 15, 20 years our body
mass indexes have continued to increase dramatically. It's
not a shift in our genetic makeup, it's a shift in our environment.
We have less physical activity, we are eating more, and
we are gaining more weight.
Is BMI a good measurement of health risk for everyone?
Or are there certain populations for whom the measurement
might not be an accurate assessment of health?
BMI is good for most of the general population. There are,
however, people with a lot of muscle-athletes for instance-who
have a high BMI but the high weight part of the equation
is more a result of muscle, not fat, and they are not at
increased risk of health problems.
There's common sense that has to come through. You can
look at someone and say, "They're in really good shape.
They have high BMI, but it's because they're fit."
And you won't see a BMI over 30 if someone is in shape.
So what are the major factors that need to be considered
in assessing someone's health risks?
We would measure their weight and their height, calculate
their body mass index, and we would measure their waist
circumference. A waist circumference lower than 35 inches
for women and lower than 40 inches for men is considered
good.
We'd also look at family history of disease. If someone
has a lot of type 2 diabetes or cardiovascular disease in
their family, that tells me they are at higher risk. We
also look at their current health. Do they have high blood
pressure? Do they have type 2 diabetes or joint pains?
We would also assess their physical activity patterns and
dietary history. That's a little bit harder to assess, but
ideally you want to get a full picture of that person. If
they are overweight but they are active and they feel really
good, they're a lot healthier than the person who is sedentary
and thinner.
What are realistic goals for lowering a high BMI?
The BMI is only related to health risk, not appearance.
Health risks start to increase as BMI gets above 25 and
dramatically increase with a BMI of 30 and above. Since
you can't change your height, the only way to shift to a
lower number in the BMI range is by lowering body weight.
They do not have to get to a BMI between 18.5 and 24.9.
If someone has a BMI of 40, it is very unlikely that they're
going to get to a BMI of 20.
But we know that health risk improves with just a mild
weight loss. Even a 5% weight loss can result in profound
health improvements. For those people who have a BMI over
30, just losing 5% is very important.
You can calculate your BMI
here
Article Source: ABCNews.com
Article Author: N/A
Net Reference 104
|
