By John Voelz – Doctor of Physical Therapy
Which Weighs More……a Pound of Muscle or a Pound of Fat?
…Trick question. They both weigh a pound.
Muscle and fat make up a large portion of our body’s tissue volume. The fat that you are able to squeeze (around your arms or waist) is more superficial fat. There is also a volume of fat that surrounds your intestines; this is called “visceral fat” and appears as a belly.
Fat is fluffy and repels water. Muscle is solid compact protein tissue that holds water. A pound of fat takes up more volume than a pound of muscle. This is why as you lose fat weight, you’re clothes fit more loosely. Gaining pounds of muscle while losing pounds of fat will change your body composition dramatically. An obese person and a bodybuilder might be the same height and weight, but their body composition is very different.
No one here is trying to be a bodybuilder, but gaining muscle tissue and losing body fat is the goal. The nice part about this is that as you gain muscle mass (with resistance exercise), you will use up many more calories from fat. This is simply because muscle tissue uses the surrounding fat as a fuel source.
Aging, hormonal changes, decreased muscle mass, and a more sedentary lifestyle all lead to increased levels of body fat as well as a differing distribution of fat contained in the body. The picture below shows the gradual change in body composition in someone who is probably aging and increasingly sedentary.
This image shows graphically how fat (yellow) is distributed in the body relative to muscle (red) in a person who weighs 250 lbs compared with someone much leaner. Notice how the fatty tissue accumulates around the sides, arms, and internal organs (forming the belly).
Different resources give different opinions regarding healthy ranges for body fat percentage. General guidelines for people over 50 appear to be the following:
Women over 50: 27% to 31%
Men over 50: 18% to 24%
The difference in genders can be explained by the fact that men have more muscle mass and women carry more internal body fat, likely for reproductive purposes.
How Do We Measure Body Fat?
There are a number of ways clinicians and scientists measure the percentage of fat that makes up your body’s total mass. A measuring tool often found in fitness centers is called a “skin caliper.” Skin fold measurements are taken and the numbers are plugged into an equation that will give you a rough estimation of your body fat percentage. This method is probably the least accurate.
In a laboratory setting, scientists will use a method called “underwater weighing,” also known as “hydrostatic weighing.” Basically, you are weighed while sitting in a big tank of water. Since muscle is dense and sinks, and fat is fluffy and floats, your buoyant weight and water displacement will tell scientists about your general body fat percentage.
“Bioelectrical Impedance” is the method we use here to measure body fat percentage. A small electric current passes through your muscle and fat tissues. Since the current travels at different speeds through muscle tissue and fat tissue, it gives us an accurate measure of each proportion.
I mentioned last week that we will be adding a very sophisticated bone density scanner this month. In addition to measuring bone density, the scanner also images and measures total body fat content. If you have any questions about the new scanner and how it will be used, please stop in and ask!