Body fat scales are devices that a person can use to measure their weight and body composition at home. The term “body composition” refers to the relative percentages of fat, muscle, and water inside the body. Understanding how much fat and muscle make up the body can be an important tool for people looking to track their overall health. In this article, we provide information on how body fat scales work and whether they give an accurate estimate of a person’s body fat percentage (BFP). We also outline alternative methods for estimating BPF. Share on PinterestBody fat scales may give a person a rough idea of how much fat is in their body. Body fat scales use bioelectrical impedance analysis (BIA) to estimate the relative percentages of different tissues and substances within the body. BIA sends a weak electrical impulse through the body. The impulse encounters varying levels of resistance or “impedance” from the different tissues and substances. The scales then use a mathematical formula that incorporates the value for electrical resistance with information about a person’s age, height, and gender. People typically supply this information via a smartphone or other electronic device. The mathematical formula then estimates the relative percentages of the following:
Fat offers more resistance than either muscle or water. As such, higher resistance values tend to result in calculations of a greater percentage of body fat. Body fat scales provide a rough estimate of a person’s BFP. However, they are not very accurate. A 2016 study found that the BIA method of measuring body composition is accurate when using standard, published mathematical formulas. However, the body fat scale that the researchers tested did not use accurate formulas to estimate BFP. Therefore, it produced inaccurate estimates. Also in 2016, Consumer Reports conducted a test of six different body fat scales. First, the researchers used a lab-based machine called a Bod Pod to take accurate body fat measurements. They then compared these results with the data that they retrieved from the home-use BIA body fat scales. In this study, the home-use body fat scales either overestimated or underestimated BFPs. The most accurate readings were off by about 21%, while the least accurate were off by about 34%. The primary advantage of using body fat scales at home is convenience. The scales are easy and safe to use. Also, as long as the scales are consistent in their measurements — even if these are inaccurate — they can help the person roughly track the effectiveness of their exercise regimen or diet over time. However, body fat scales are not an accurate method for estimating BFP. According to doctors, they typically overestimate or underestimate BFP by a large amount. Home body fat scales also cannot show where a person’s body fat is stored. The location of body fat is an important consideration when assessing a person’s susceptibility to disease. For instance, a 2016 study found an association between increased abdominal fat and a higher risk of developing cardiovascular disease. Body mass index (BMI) uses a person’s height and weight to get a general idea of whether their weight is likely to affect their health. According to the Centers for Disease Control and Prevention (CDC), BMI is a good tool for screening whether a person is underweight or overweight. However, it does not measure body fat directly. BMI also does not take into account a person’s muscle mass. Exercise can help a person lose fat and gain muscle. As muscle is denser than fat, a person’s body weight may actually increase as a result of exercise. A person could use both BFP values and BMI values to help guide their dietary and exercise choices. If either value is higher than average, a person should see their doctor. Higher values could indicate an increased risk of cardiovascular disease. Having a BMI or BFP below the recommended range also has health risks. A person can use several different methods to estimate their BFP. Some are suitable for use at home or in a doctor’s office, but others must take place under tightly controlled laboratory conditions. Typically, the most expensive options provide the most accurate estimates. At-home optionsSome methods that people can use to estimate their body fat at home include: CalipersCalipers are tools that measure the distance between two sides of an object. A person can use calipers to measure the thickness of skin folds on different parts of the body. The accuracy of caliper measurements depends on the experience of the person using them. Handheld BIA devicesHandheld BIA devices use electrical impulses to estimate BFP. As with step-on body fat scales, they are not very accurate. Laboratory optionsThe following body fat measurement tools require special machinery and provide much more accurate results: Bod PodA Bod Pod is a machine that calculates a person’s body density. It does this by combining two measures: a person’s mass or “weight” and their volume. A person sits inside the Bod Pod, which uses highly accurate scales to measure their weight. Meanwhile, special sensors detect the volume of air that the person’s body displaces based on air pressure changes that occur in the Bod Pod. This value represents the person’s body volume. The Bod Pod uses the weight and volume values to calculate the person’s body density. A technician can then use a mathematical formula to estimate the person’s BFP. A Bod Pod requires specially trained operators, who tend only to use it in research laboratories. Hydrostatic underwater weighingHydrostatic underwater weighing (HUW) calculates a person’s body density and body volume to estimate their body composition. HUW works by comparing a person’s weight on dry land with their weight underwater. It also measures the volume of water that a person’s body displaces when they sit inside a tank of water. The above values make it possible to determine the person’s body composition, including their BFP, based on the principle that fat is less dense than muscle. As with the Bod Pod, HUW is typically only available in research laboratories and university settings. Body fat scales are not very accurate at estimating a person’s body fat percentage. However, they may provide a rough idea of how much fat a person has in their body. Together, body fat scales and BMI can give a general indication of a person’s health. If either value is high, a person should see their doctor for a health check. The doctor can also provide advice on diet and exercise.
Do you have a love-hate relationship with your bathroom scale? The bathroom scale may be a good tool for measuring weight, but it may not accurately reflect your true health. Body composition takes your weight measurement one step further, figuring out what percentage of your weight comes from fat, muscle, and bone. The difference between fat mass and non-fat mass (muscle and bone) paints a more complete picture of your health and fitness.
This article reviews the basics of your body composition, what it means, and what you can do about it. Your body composition determines what percentage of your total body weight comes from fat, muscle, and bone. Knowing your body composition provides more detailed information about your health. Two people can weigh the same, but have very different wellness and fitness needs because of their body composition. Body composition is important because it measures your overall health and fitness level in terms of your body fat percentage. Your bathroom scale can’t tell the difference between how much of your weight comes from fat and how much from muscle. But body composition measurements can.
Less fat and more muscle tends to point toward a better level of health. Body fat includes all the stored fat in your body. There are two types of body fat:
In addition to insulating and protecting your body, fat provides energy, carries fat-soluble vitamins, makes certain hormones, and serves as a building-block for cell membranes. You need a certain amount of body fat to perform these functions—this is known as essential fat. Body fat percentage is the percent of fat that makes up your total body weight. Many factors influence your body fat percentage, including sex, age, fitness level, and lifestyle.
The body fat percentage ranges come from the American Council on Exercise (ACE).
Athletes tend to have a lower body fat percentage than people who are physically fit because having less fat improves their athletic performance. However, when body fat percentages dip too low, athletic performance suffers and immune function declines. On the flip side, a body fat percentage that’s too high is a risk factor for chronic illnesses like diabetes, high blood pressure, and heart disease. Body composition and body mass index (BMI) are tools that assess body fatness. However, the methods used to measure body composition and BMI differ. Additionally, BMI may not provide accurate results in all situations. Health professionals use the BMI to assess an individual's risk for disease based on their body fatness, or where they fall on the BMI table. But recent evidence suggests that the BMI is a very poor measure of body fatness and disease risk, and may not serve as the best—or only—metric for measuring body composition and health.
Body Mass Index (BMI) is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnicity, race, gender, and age. Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes. BMI is a tool that has been used by health professionals to assess body fatness and health. It’s a mathematical equation that compares your weight to your height.
For example: (150 pounds)/(66 inches x 66 inches) X 703 = 24 This BMI table is from the Centers for Disease Control and Prevention (CDC).
You don’t need any special equipment to measure BMI, making it a quick tool to assess body fat and health. However, the BMI isn’t perfect and may not accurately assess body fatness in all people. For example, a bodybuilder may have a BMI that puts them in the overweight category, but have a low body fat percentage. There are a number of ways to measure body composition. However, you need more than a bathroom scale and calculator to figure out what percentage of your weight comes from fat and what percentage comes from muscle. Bioelectrical impedance (BIA) is a tool that estimates your body composition by measuring your body’s resistance to a low-level electric current, or impedance. Muscles have a lower resistance to an electric current than fat.
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Skinfold measurements involve the use of special calipers that measure the skinfold—subcutaneous fat—on different parts of your body. Fitness trainers use skinfold measurements to assess body fat because it’s quick and convenient.
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The DEXA scan, or dual-energy X-ray absorptiometry scan, uses a low-level X-ray to measure bone, muscle, and body fat.
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Hydrostatic weighing involves full submersion in a water tank, using water displacement to measure body composition. Since fat floats and muscle sinks, a person with more lean body mass weighs more underwater.
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Bod pod is similar to hydrostatic weighing, but uses air displacement instead of water displacement to measure body composition. For this test, you sit in an egg-shaped chamber, which uses your body weight and volume to determine your body composition.
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Body composition provides valuable information about body fat percentage. However, your body shape is unique to you and there are uncontrollable factors that affect your body composition including:
To change your body composition, you need the right balance of physical activity and nutrition to reach your goals. Slow and steady changes work best when you want to increase muscle and lose fat. It's important to remember that some factors will remain out of your control.
Before making any changes to your diet or workout routine, consult with your primary care provider or a registered dietitian for guidance. Your body composition may help you better understand your current level of health and fitness. It can also serve as a measuring tool to monitor progress when starting a new fitness or wellness program.
When trying to change your physique to improve your fitness level, it’s important to implement a safe and effective workout routine and a balanced eating plan. Seek advice from a health care professional before making any major changes to your diet or exercise routine. Frequently Asked Questions
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