How Accurate Are Body Fat Scales?

While stepping on a scale is perhaps the easiest method of body fat measurement, there are other ways you can determine your body fat percentage. Aside from BMI, you can ask your health provider about the following methods:

Waist measurements

One drawback to body fat scales is that they don’t tell you how much fat your body is holding around the waistline, which is considered a risk for:

  • cardiovascular diseases
  • type 2 diabetes
  • fatty liver disease

Measuring your waistline can help complement your body fat scale results.

The National Heart, Lung and Blood Institute notes that your risk for heart disease and diabetes increases if you are a woman with a waist measurement greater than 35 inches (88.9 cm) or a man with a waist measurement of more than 40 inches (101.6 cm).


Often used by fitness professionals, calipers are used to literally pinch your skin folds (usually around the waist or hips) to estimate your body fat.

The accuracy of this method varies. Results may be more or less accurate depending on the expertise of the person taking the measurement.

Shop online for body fat calipers.

Dual-energy x-ray absorptiometry (DEXA) scans

Often used to measure bone mass for osteoporosis diagnoses, DEXA scans are also reliable methods of body fat measurement and can be more reliable than relying on BMI alone.

To get one of these scans, you’ll need to find a center that has the equipment. The scans can be pricey depending on your location and may not be covered by insurance.

Handheld fat measurement devices

This body fat measurement test works similar to that of a scale, except it doesn’t measure your weight. There are sensors on either side of the device that measure your body fat as you hold the device in front of you.

Handheld fat measurement devices aren’t as accurate as other methods, but they’re easy to use and relatively inexpensive.

Shop online for handheld fat measurement devices.

Underwater weight (hydrodensitometry) test

This test is based on the buoyancy of your body weight. Fat floats more easily than muscle. Based on your buoyancy and your weight, the person administering the test can calculate your body fat percentage.

Underwater testing is considered to be an accurate tool for measuring body fat. However, it can be difficult to find a center that has the ability to do this type of testing. The test can also be uncomfortable.

Bod Pod

Available at some fitness centers and medical facilities, a Bod Pod is a device you stand in for a few minutes while it measures your body fat via air displacement plethysmography (ADP).

This method has similar accuracy when compared to underwater testing. However, access to these devices is limited, and testing can be expensive.

Body Fat Scales – Do They Really Work?

By : Jodie Shield | | On : January 8, 2013 | Category : Great Gadgets

By: Jodie Shield, RD

Many of you have asked me what I think about body fat scales – are they accurate? What’s the best one to buy? Do they really measure body fat? Well I confess: my favorite scale – if there is such a thing- is the doctor’s office upright scale. You simply step on, slide the markers until they balance, then read your weight. However, I realize this type of scale doesn’t tell you your body fat, BMI or any of the other handy measurements many of us want to know so we can analyze our weight and health. So I went undercover to my local Bed, Bath and Beyond store and bought a body fat scale. Here’s what I discovered . . .

My first dilemma: so many scales to choose from! Since I use to write for Weight Watchers and love their updated eating plan, I bought one of their body fat scales and decided to give it a try. This particular scale provided five key measurements: weight (in pounds), body fat weight, body fat percentage, body water, and bone mass. In addition, it contained enough memory to allow me to program the scale for up to four users. Check out my review of the Weight Watcher scale at the bottom of this article.

How do body fat scales Work? Most of these types of scales use bioelectrical impedance. That is to say, they send a safe and very low electrical current through the lower half of the body. Since the electrical current flows more quickly through water and muscle than bone or fat, the scale measures the speed of the current. Then based on that number, the scale estimates body fat using a multi-step, mathematical formula. One thing you will want to be aware of which was new to me: if you are pregnant or have an electrical implant such as a heart pacemaker or defibrillator these scales are not recommended.

Are body fat scales Accurate? Good question but the answer depends on several things. Body fat scale readings can be thrown off by the following factors. In addition,the results may not be accurate for kids under the age of 16, or people with an elevated body temperature, diabetes or other health condition.

  • Hydration. If you’re dehydrated or sweat a lot from exercise or your climate, you will have less body water for the electric current to flow through. The result: your body fat reading may be higher than it really is. And the opposite is also true. If you drink too much fluid, have a full bladder, or if you are a women experiencing water retention from your menstrual cycle, your body fat reading may be lower than it really is. For best results: be aware of what affects your fluid retention; weigh yourself once a week, on the same day and at the same time of day; wear the same clothes or none at all.
  • Movement. The electric sensors in these scales are sensitive and work best when weighing stationary objects. Wiggling around or quickly hoping on the scale can interfere with your reading. For best results: always stand on the same area of the scale platform and stand still.
  • Foot calluses. Some studies have found that having thick calluses on your feet may prevent the electric current from flowing accurately. For best results: shave those calluses. (Did anyone say pedicure?)
  • Muscle. Heavy-duty weight training builds muscle which weighs more then fat. This can result in a higher body weight measurement which can throw off the arithmetic in the body fat and BMI formulas (To calculate BMI, visit my home page.) For best results: if you do a lot of resistance weight training, these scales may not be your best option.

Great Gadget Review for:

Weight Watchers Conair Body Fat Scale (model #WW78)

Pros: I was pleasantly surprised how accurate the Weight Watchers body fat scale was for me. My weight was spot on, BMI correct, and my body fat percentage matched the reading I had confirmed by a personal trainer at my local health club. The initial set up took awhile, but after that using the scale was quick and easy. And it was fairly inexpensive $29.99. (The majority of body fat scales ranged between $30-$50 dollars.)

Cons: The five different readings flashed by way too quickly. And I had no clue what they meant. The owner’s manual came with some excellent charts which I would recommend you hang nearby or keep handy.

Healthy Eating For Families Recommendation: 4 out of 5 stars

Post Views: 149,523

Weight is usually one of the first topics that come up in discussions about personal health. But the number you see when you step on the scale doesn’t tell the whole story about how healthy (or unhealthy) you may be.

Those looking for a clearer picture of what their weight really means in relation to their health may want to take a look at metrics other than weight. One of these metrics is the body mass index, or BMI, an estimation of body fat that can be calculated using a person’s height and weight. Health-conscious individuals might also want to know more about their body composition, which refers to the proportion of fat tissue you have, relative to lean tissue (muscles, organs, etc.).

Health care professionals use BMI, as well as advanced body composition tools, including special X-ray machines, to assess their patients’ risk factors for certain weight-related health conditions. And anyone can use readily available tools — such as online BMI calculators, skinfold calipers and bioelectrical impedance devices — to better assess their health and physical fitness from the comfort of their own home.

What is BMI?

The body mass index is an estimation of a person’s body fat, according to the National Institutes of Health. To calculate BMI, divide your weight (in pounds) by your height (in inches) squared, and then multiply that number by a conversion factor of 703. This same calculation can be used when measuring weight in kilograms and height in meters, but no conversion factor is needed.

For most individuals, a BMI between 18.5 and 24.9 means that their weight is normal, or “acceptable,” according to the Centers for Disease Control and Prevention (CDC). A BMI between 25.0 and 29.9 means a person is overweight, and those with a BMI over 30.0 are considered obese.

Those whose BMI puts them in the “overweight” category should consider losing weight if they also have two or more health risk factors, such as smoking, inactivity or high blood pressure, according to Katherine Tallmadge, a registered dietitian and author of the book “Diet Simple: 195 Mental Tricks, Substitutions, Habits & Inspirations” (Lifeline Press, 2011).

“The evidence is solid that the risk for various cardiovascular , cancer, arthritis and other disease starts to rise at a BMI of 25,” Tallmadge told Live Science, “This is why experts try to encourage people to be at a BMI between 18.5 and 24.9. Men tend to be at the higher end of the scale and women toward the middle and lower end, but your desired weight may vary depending on your personal health goals.”

Body fat

Knowing your BMI can give you an idea of how healthy your weight is. However, this metric isn’t a reliable tool for everyone. Athletes and people with a muscular physique may have a BMI that would classify them as overweight or even obese, even though they are clearly fit. This is because a BMI doesn’t distinguish between what percentage of a person’s total weight is composed of muscle and what percentage is fat, according to the CDC.

BMI is also not always a reliable metric for those who fall into the “normal” weight category. It’s possible to have a normal weight status but still have an unhealthy amount of fat compared to lean muscle, according to New York University’s Langone Medical Center, which lists several methods for finding out how much of your total body weight is made up of fatty tissue — a metric known as body fat percentage. These include:

  • Dual energy X-ray absorptiometry (DEXA) scan: Used in research institutions and health care facilities to measure bone density, DEXA scans calculate body fat by subtracting the weight of lean soft tissue in the body from a person’s total weight.
  • Hydrostatic weighing: Commonly known as underwater weighing, this method involves submerging a person in water to calculate the mass per unit volume of his or her body. Like DEXA scanners, the tanks used for hydrostatic weighing are usually found at universities and health care facilities and are not always available to the public. However, some fitness and health care facilities do offer this type of body composition testing for a fee.
  • Air displacement plethysmography (ADP): Similar to underwater weighing, this method uses displaced air (rather than displaced water) to calculate a person’s mass per unit volume. One popular version of this test is the Bod Pod, an ADP machine that can be found at many fitness and research facilities.
  • Bioelectrical impedance analysis (BIA): One of the most accessible ways to measure your body fat percentage at home is with a BIA device, many of which are sold as scales or handheld devices. Such devices send a tiny electrical current through your body (so tiny you don’t even notice it). By measuring the impedance, or opposition, to this current through your body, the devices can estimate your total body water. This measurement can then be used to estimate both lean mass and body fat percentage.
  • Skinfold calipers: This low-tech solution to measuring body fat involves using a handheld instrument known as a caliper to measure the thickness of folds of skin on different parts of the body. These measurements can then be plugged into a variety of equations to calculate body fat.

Each of these methods for measuring body fat has its pros and cons, but the only options for home use are bioelectrical impedance analysis and skinfold calipers. The measurements you get with a BIA device can fluctuate dramatically depending on how much water is in your body. For this reason, you should use the device under the same conditions every time you want to measure your body fat (e.g., in the morning, after having one glass of water but nothing to eat). Skinfold calipers may provide more accurate body fat readings at home, but you’ll need to practice to become proficient in how to use them, according to the DailyBurn, a health and fitness website.

Regardless of how or if you choose to measure your body fat, you should always speak with your doctor before undertaking a weight loss plan, according to Tallmadge. He or she will be able to give you more information on how to safely lose weight and how to maintain the proper diet and exercise routine to keep the weight off, she said.

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+.

Additional resources

  • More information on body composition and testing can be found at the American Heart Association.
  • More information on risk factors for health conditions associated with obesity from the National Institutes of Health.
  • Comprehensive information about health and weight from the University of California, Berkeley.

Professional Scales

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As the world-leader in providing accuracy and reliability for consumers, Tanita scales are more affordable for consumers than DEXA (dual energy X-ray absorptiometry) or hydrostatic weighting, and more convenient and private than skin fold (calipers) tests. Our consumer scales allow for personal, in-home monitoring, detailed analysis of diet, and exercise and weight loss progress, while also offering modern design. Tanita scales feature multiple person memory with recall, sleek glass platforms with transparent electrodes, and a low profile. They are ISO 9001 certified and measure in both pounds and kilograms.

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