Determining calorie needs part
of dietitian's job
January 24, 2005
By Mary C. Koch
Dietitians are known for being able to determine a
person's calorie needs. It's a huge part of our job.
If calories didn't matter, then we wouldn't be facing
the current obesity epidemic in our country. So, have
you ever wondered how those of us in the profession
figure out how many calories you need? Well, you're
in luck!
Do a search on the internet about how to determine
your personal calorie level and you'll come across pages
of helpful information. There's everything from fill-in-the-blank
forms to worksheets you print out and fill out on your
own.
Personally, I use an equation known as the Harris Benedict
Equation (HBE), which has been proven over time to provide
a fairly accurate measurement of a person's basal energy
expenditure (BEE).
The HBE takes into consideration your age, height and
current weight. BEE represents the number of calories
that you need to meet your minimum calorie needs to
keep your body running at its most basic level. And
since most of us aren't comatose, the Harris Benedict
Equation uses activity factors to account for getting
out of bed and moving around, exercise and illness.
There are more simple ways of calculating calorie needs
based solely on a person's weight. For example, I will
use 25 calories per kilogram of actual weight to get
a baseline weight loss calorie need, 30 calories/kg
for weight maintenance and 35 calories/kg for weight
gain. These are quick and dirty ways to avoid long calculations,
but they aren't always the most reliable. Certain conditions
such as exercise level, percentage of overweight and
chronic health conditions can make these easier calculations
less exact.
In general, most methods of estimating calorie needs
are going to be in the ballpark, but there are always
instances that will be exceptions. If a person is very
muscular and has a very high amount of lean body mass,
the usual calculations tend to be less accurate and
can be less than the person's actual needs. The opposite
is usually difficult as well.
The more body fat, the more adjustments need to be
made to get the best picture of the actual number of
calories needed to maintain or even lose
weight. Then there are conditions such as cancer
and pulmonary diseases that pose their own challenges.
Recently, I have had the opportunity to use an indirect
calorimeter to measure personal calorie needs. This
instrument measures the volume of oxygen that is consumed
over a ten minute period, giving a very accurate measurement
of anyone's personal calorie needs. Although this method
is a bit more involved than using a calculator, I am
very excited about using this method both clinically
and in the community. For someone who has been struggling
with their weight, up or down, this can be a very important
key to unlocking the mystery and achieving their goal
weight.
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