Body weight is a difficult measurement to track when you’re trying to lose excess weight or get in shape. Your day-to-day weight is influenced by genetics, diet, and environmental factors. After several weeks of losing weight, seeing a weight loss plateau or gain can be extremely frustrating.
As you exercise, your body composition changes. You gain muscle mass and lose fat, a healthier change, but your weight may stay the same or even increase by a couple of pounds. Body composition is far more important to your overall health than body weight.
For this reason, it is better to combine several measurements to get a better idea of how your body composition is changing as you get healthier and stronger! Keep in mind that these are just numbers that can change from day to day; keep an eye on the trends to get feedback on your efforts.
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Body mass index (BMI) is a quick measurement that considers the ratio of weight to height. It does not differentiate between fat mass and muscle mass.
BMI is more useful for screening populations and tracking trends. Obesity is a major risk factor for cancer, type 2 diabetes, and heart disease, among other diseases. Experts have found that people have an increased risk of mortality at a BMI of 25 kg/m2 or higher. Keeping track of a population’s average and range of BMI can tell you a lot about that population’s health, but it isn’t as helpful when monitoring an individual’s overall health.
In 2016, the United States Equal Opportunity Commission proposed rules that would allow employers to charge employees up to 30% more for their health insurance if they reached a certain BMI. They assumed there was a direct relationship between higher BMI and poor health. Researchers found that nearly half of the participants in the study were classified as overweight or obese but were metabolically healthy. Using a single number to determine overall health is ineffective.
Muscle mass is a measurement of skeletal muscle, the muscle that you work hard to increase in strength and flexibility when exercising. Muscle burns more calories at rest than fat. It is always remodeling and repairing itself.
Fat, or adipose tissue, is important to your overall health as well. It
Everyone’s body shape is different; target numbers don’t consider:
To track changes in your body composition over time, use several measurements to gauge your progress when using a diet, exercise, or treatment plan to manage your weight.
One of the most commonly used measurements for body composition is body mass index (BMI). It is easy to measure. All you need is your height and weight. The problem is that it doesn’t consider body composition at all.
To better understand how BMI is flawed, consider Jen and Marcy.
Jen exercises regularly. She is an amateur weightlifter and lives in her CrossFit gym. Jen is 5’4″ tall and weighs 147 pounds. Her BMI is 25.2, which is considered overweight. BMI does not consider that Jen’s muscle mass makes up a large percentage of her body mass.
Marcy hates the gym and exercises as little as possible. Marcy is also 5’4″ and weighs 140 pounds. Her BMI is 24, which falls within the healthy range.
But who is really healthier, Jen or Marcy?
The formula for BMI is weight (lb) / [height (in)]2 x 703
To calculate your BMI, take your weight in pounds and divide it by your height in inches squared. Then multiply the result by a conversion factor of 703. Another option is to use a BMI calculator.
|BMI (weight in kg/height in m2)||Classification by the World Health Association (WHO)|
|Below 18.5||Below the reference range|
|> 40.0||Class III|
Calculating BMI is a quick measurement that is frequently tracked in doctors’ offices, but calculating body fat and muscle mass provide more useful numbers to track as you work to change your body composition.
It is difficult to measure muscle mass. However, lean body mass can be calculated by subtracting body fat percentage from 100%.
Body fat distribution can be as important when assessing your health as the amount of excess body fat you are carrying. The blood vessels draining abdominal fat enter the liver. Byproducts of metabolism that come from abdominal fat enter the liver and skeletal muscles easily. This makes insulin resistance more likely.
Reducing abdominal fat decreases your risk of diabetes and cardiovascular disease. Researchers found that having a wider waist size and a higher waist to hip ratio, especially for women, can be a better predictor of heart attack risk than BMI.
Measuring your abdominal circumference is the simplest way to measure body fat at home and track your progress when changing your body composition.
Waist sizes greater than 40 inches in men and 35 inches in non-pregnant women are associated with an increased risk of heart disease and type 2 diabetes. However, waist size alone can’t tell you your body fat or lean mass percentages.
Take your measurement first thing in the morning to reduce the effect of gases and liquids in the GI tract. Stand with your feet positioned together. Measure your waist circumference midway between the bottom of your ribs and your hip bones. Wrap a non-elastic measuring tape firmly around your waist. It should be snug but not constricting. Take your measurement after you breathe out (exhale).
To measure your waist to hip ratio, measure your waist midway between your ribs and hips and your hips at the widest part of the hips and buttocks.
The World Health Organization classifies waist-to-hip ratio as follows:
Waist circumference and waist-to-hip measurements are data points that can help you determine whether you may be carrying excess abdominal fat. Losing excess belly fat can help reduce your risk of cardiovascular disease, type 2 diabetes, and premature death.
People use several methods for losing excess weight, including making changes in diet without exercise, increasing exercise to build more muscle or a combination of both. Whichever strategy you choose, the important thing is that you are working on improving your health!
In addition to waist and hip measurements, you can track other body circumference measurements. Consider tracking some or all of the following:
A calculator based on the U.S. Navy Method can help you calculate body fat using these measurements:
Once you have a body fat measurement, subtract it from 100% to get lean body mass.
According to the American Council on Exercise (ACE), these are reference ranges for body fat:
Body fat scales use bioelectrical impedance to measure total body water, fat-free mass, and fat mass. A painless electrical current is sent through the body. Body fat estimates are based on how long it takes for the signal to return to the sensor. Electrical current moves more slowly when there is more body fat because there is more resistance to flow. This is called increased impedance.
Body fat results using impedance scales may vary based on hydration status. They also use statistical equations that might only be right for very small groups of people. Whether fat is carried more in the abdomen or distributed throughout will affect how well these tools can measure body fat.
Skinfold calipers are an inexpensive and easy way to estimate body composition and calculate body fat and are commonly used by trainers. Using the skinfold calipers, the skin is lightly pinched in different places on the body.
Skinfold measurements are based on the premise that about half of all body fat is under the skin. The error rate for skinfold measurements is about 3.5%. Skinfold caliper measurements must be taken at consistent sites by someone with the proper training to get accurate results.
A dual-energy X-ray absorptiometry scan (DEXA) uses low-level X-ray to determine body composition. The two energy levels used in a DEXA scan help differentiate between body fat, bone, and other soft tissues. The scan takes about 20 minutes and requires a small amount of radiation exposure.
Hydrostatic weighing involves being submerged in a water tank. The amount of water your body displaces is measured and used to calculate body composition. Since fat is more buoyant than muscle, a person with a higher percentage of lean body mass will weigh more than someone with a higher fat percentage. To get an accurate measurement, you must be able to put your whole body under water.
These measurement techniques are used in research and training facilities. Keeping track of your waist circumference, weight, and maybe even your bioimpedance measurements should provide you with the information you need to calculate your body fat and muscle mass at home and track your progress toward a healthier body composition.
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While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.