Body composition is more
important than weight loss
A main theme for this year has been the importance of reducing excess body fat rather than focusing on
losing body weight. Most dissatisfaction is about being too fat and how that looks, rather than being any
particular weight. The difficulty is in finding a meaningful method to measure body composition and changes
that occur through diet and exercise.
The two common methods are skin-fold measurements using calipers and BIA (bioelectrical impedance
analysis) such as Tanita scales. Both these techniques are unreliable.
Calipers rely on a technician taking pinch tests from a number of different sites. The percentage of body fat
is calculated using a table. Some of the pinch sites, such as the thigh in females are difficult to measure
accurately. Variables such as hydration levels and muscle mass make consistency between tests difficult.
There is difficulty in getting consistent results with different technicians. The tables used for calculations
also vary considerably, depending on what population they were originally designed for. Many tables were
formatted in university laboratories and are only relevant for young white American athletes. They do not
transfer well to other groups.
BIA is now common in gyms and is often incorporated in body weight scales for home use. This looks very
high tech as electrodes are attached usually via a hand and foot. Some data is entered such as your height
and weight. The machine then runs a current from one electrode to the other. BIA works by estimating
total body water. Water is conductive and different tissues such as bone, muscle and fat all contain different amounts of water. By measuring how fast the current moves from one electrode to the other, the
machine calculates your body-fat percentage by measuring how much water is present. The drawback with
this method is that results will vary depending on hydration. Results can change significantly with a drink of
water or urinating, pre or post measurement.
Gyms often include BIA as part of their nutrition and exercise packages. Clients are often provided with low
calorie (under 2000 calories a day) or low carbohydrate diets. The water loss from these diets can range
from 90% in the first week to 60% by the third week. What looks like a change in body fat percentage is
really only a change in water balance.
Another method of calculating changes in body-fat is by taking circumference measurements and using
comparative tables. This is reasonably simple to do and gives some useful feedback. Because body-fat is
less dense than muscle, it takes up more space so if you replace a kilo of body fat with a kilo of muscle, you
will weigh the same, but be smaller in size.
Remember we are all different. Copying the same programme as someone with a different body type will
only lead to frustration. I encourage you to focus on your own body and not to compare yourself to others.
Exercise regularly, lift some weights, keep mobile, get lots of rest and make sure that your diet is based
around plenty of fresh vegetables, some fruit and lean protein. Enjoy the treats – but in moderation.
© Susan Birch 2010
www.truefit.co.nz