The weight you see on your bathroom scale says nothing about your body composition. You can be of normal weight and still have a high ratio of fat to muscle. That’s why it’s important to know your body composition – how much of your weight is fat and how much is muscle. The best way to do that is to measure your body fat.
Options for Measuring Body Fat
One of the most accurate ways to measure body fat is using a DEXA scan. This involves scanning the body using low-dose x-rays. Not only is this method expensive, but it also involves exposure to radiation. Another accurate way to measure body fat content that doesn’t involve radiation is hydrostatic weighing. With this method, you’re weighed both on land and in a tank of water. Unfortunately, most gyms don’t have an underwater weighing tank to offer this service, although some universities do. You can also use skin calipers to measure skin-fold thicknesses at five different areas of the body to estimate body fat. This method is prone to error if not done properly.
Fortunately, there’s another way to measure body fat. Some companies sell body fat scales that measure body fat using the principle of bioelectrical impedance. With this method, you stand on a body fat scale, and it sends a weak electric current from one side of your body to the other -from foot to foot. Muscle conducts electrical current more rapidly than fat does, so the machine will measure the speed of conduction through your limbs to approximate your body fat percentage. It’s certainly a lot easier than being submerged in a water tank.
How Accurate Are Body Fat Scales?
Body fat scales are reasonably accurate if you use them under controlled conditions. Body fat readings on the scale are sensitive to how well hydrated you are. When you wake up in the morning and you’re dry from lack of fluids, your body fat reading will be higher. As you drink more fluids throughout the day, the reading usually falls. Even though there are variations in the readings based on hydration, body fat scales are a good way to monitor changes in body fat percentage over time, but you need to weigh at the same time every day under similar conditions.
To get the most accurate reading using a body fat scale, weigh yourself in the morning after drinking a cup of water and before eating breakfast. Keep the scale in a room that stays at a constant temperature. Temperature can affect how rapidly the electrical current moves from foot to foot. Don’t weigh after stepping out of the shower, and wipe your feet dry if they’re damp from perspiration. Water can alter how rapidly the current is conducted and alter the results. Keep any moisture or oils from the scale before stepping onto it. Don’t weigh after exercising, because you’ll probably be dehydrated. The scale allows you to set up a user profile that includes information such as your sex and height. Make sure this information is accurate since it can alter the results you get.
Should You Get a Body Fat Scale?
A body fat scale isn’t as accurate as a DEXA scan or underwater weighing, but you can use it to follow changes in your body fat percentage. Using a body fat scale, you’ll get an idea of how well your workout is working and whether you need to make changes. You can get a good quality body fat scale for under $100, and it will give you a more accurate picture of your body composition than the bathroom scale will. For many, it’s worth the investment.
The Nutritionist. Robert Wildman, Ph.D., RD. 2002.