Your body composition is the relative proportions of fat and lean tissue found on your body. Learn how body composition is evaluated using methods such as bioelectrical impedance analysis and the waist-to-hip ratio.
I'm sure you have heard that obesity is a growing problem around the world. In fact, most researchers say it has become an epidemic. But what exactly is so wrong with carrying around these extra pounds?
Well, as it turns out, having too much body fat creates problems from your toes on up. The excess weight stresses your joints and increases the risk of developing arthritis in your feet and knees. High amounts of fat have been linked to gynecological problems in women. We also see high body fat linked to conditions, such as type 2 diabetes, gallstones, asthma, heart disease and even depression. While some body fat is needed for the body to function properly, having too much moves you into the overweight category and affects your health.
Your body weight is the sum of the amount of fat on your body plus the amount of lean tissue you carry. Lean tissue consists of pretty much everything but fat, so your muscles, bones, organs and tissues are considered part of your lean body mass. We use the term body composition to refer to the relative proportions of body fat and lean tissue on a person's body. By measuring body composition, we can determine if a person is negatively affecting their health by carrying around too much body fat. In this lesson, we will take a look at two methods used to estimate body composition: bioelectrical impedance analysis and waist-to-hip ratio.
Bioelectrical Impedance Analysis
When it comes to body fat, men and women are not created equal. In general, women carry more fat than men. Women need this extra fat for reproductive reasons. Therefore, we see that women need to carry between 10 and 13 percent body fat for essential purposes. For a man, the essential range is between two and five percent.
Body composition can be measured using techniques like bioelectrical impedance analysis, or BIA, which is a method used to estimate a person's body fat percentage using a small electric current. This method is easy to perform and harmless. The analysis measures how easily the current moves through the tissues of your body. It involves electrodes attached to various parts of your body or a simple device that is either held in both hands or stood on with both feet. Does your bathroom scale analyze your body fat percentage? If it does, then it's using bioelectrical impedance. When you contact the device, you complete a circuit in which the electric current can flow.
The test is able to distinguish lean tissue from fat because the current will move more easily through your lean tissues. Lean tissues are high in water, which is easy to pass through, whereas fat slows, or impedes, the movement of the current. To keep this straight, think of swimming through a pool of water compared to swimming through a pool filled with fatty liquid, like vegetable oil. There would be more resistance in the oil pool.
While this test is quick and easy, the fact that it's based on the water content of your body can make it inaccurate. For instance, if you were working outside on a hot summer day, the sweat you lose could cause your body water level to be lower than normal. This would show up on a BIA test as a lower amount of lean tissue and record an artificially high body fat percentage.
We learned that having too much body fat is a health risk, but there is more to the story. As it turns out, where your body stores this fat can also affect your health. There are two types of fat stored on the body: subcutaneous fat is adipose tissue deposited under the skin, and visceral fat is adipose tissue deposited around the organs of the abdomen. These are easy terms to keep straight if you remember that 'subcutaneous' literally means 'below the skin' and 'visceral' means 'organ'. We see that fat located in the lower body is subcutaneous fat, whereas fat in the abdominal area tends to be more visceral fat. This is important because subcutaneous fat does not increase health risks as much as visceral fat. Therefore, your health is more negatively affected by a big belly than big hips. In other words, it's better to be shaped like a pear than an apple.
To evaluate health risk associated with body fat location, we use a measurement known as the waist-to-hip ratio, or WHR. This is a measure of the waist circumference divided by the hip circumference. This is a simple test that can be determined using nothing more than a tape measure. For example, if a woman has a waist circumference of 29 inches and a hip circumference of 38 inches, then her waist-to-hip ratio would be .76. This woman would be in the low risk category. Basically stated, a higher ratio equals a higher risk of developing a disease, like diabetes and heart disease. For women, a high risk is a WHR > .80. For men, a high risk is a WHR > .95.
Let's review. Measurements of body composition, which is the relative proportions of body fat and lean tissue, can be used to evaluate your risk of disease. Bioelectrical impedance analysis, or BIA, is a method used to estimate a person's body fat percentage using a small electric current. The test is able to distinguish lean tissue from fat because the current will move more easily through your lean tissues, due to their higher water content.
We learned that the location of body fat can affect your health. Subcutaneous fat, which is adipose tissue deposited under the skin, does not impact your health as much as visceral fat, which is adipose tissue deposited around the organs of the abdomen. To evaluate health risk associated with body fat location, we use a measurement known as the waist-to-hip ratio, or WHR, which is a measure of the waist circumference divided by the hip circumference.
After this lesson, you should have the ability to:
- Define body composition
- Explain the reasoning behind bioelectrical impedance analysis and waist-to-hip ratio for measuring body composition
- Describe how both measurements are performed
- Differentiate between subcutaneous fat and visceral fat
- Identify the healthy waist-to-hip ratios for men and women