Body fat can be measured in several ways, with each body fat assessment method having pros and cons. Here is a brief overview of some of the most popular methods for measuring body fat-from basic body measurements to high-tech body scans-along with their strengths and limitations.

Adapted from 1. Like the waist circumference, the waist-to-hip ratio WHR is also used to measure abdominal obesity. Equations are used to predict body fat percentage based on these measurements.

BIA equipment sends a small, imperceptible, safe electric current through the body, measuring the resistance. The current faces more resistance passing through body fat than it does passing through lean body mass and water. Equations are used to estimate body fat percentage and fat-free mass.

Individuals are weighed in air and while submerged in a tank. Fat is more buoyant less dense than water, so someone with high body fat will have a lower body density than someone with low body fat. This method is typically only used in a research setting. Different BIA analysers may vary.

Population-specific equations are available for some instruments, which are only reliable for specific ethnic groups, populations, and conditions. Population-specific equations may not be appropriate for individuals outside of specific groups. There exist various anthropometric methods for estimating body fat.

The term anthropometric refers to measurements made of various parameters of the human body, such as circumferences of various body parts or thicknesses of skinfolds.

Most of these methods are based on a statistical model. Some measurements are selected, and are applied to a population sample.

For each individual in the sample, the method's measurements are recorded, and that individual's body density is also recorded, being determined by, for instance, under-water weighing, in combination with a multi-compartment body density model.

From this data, a formula relating the body measurements to density is developed. Because most anthropometric formulas such as the Durnin-Womersley skinfold method, [18] the Jackson-Pollock skinfold method, and the US Navy circumference method, actually estimate body density, not body fat percentage, the body fat percentage is obtained by applying a second formula, such as the Siri or Brozek described in the above section on density.

Consequently, the body fat percentage calculated from skin folds or other anthropometric methods carries the cumulative error from the application of two separate statistical models. These methods are therefore inferior to a direct measurement of body density and the application of just one formula to estimate body fat percentage.

One way to regard these methods is that they trade accuracy for convenience, since it is much more convenient to take a few body measurements than to submerge individuals in water. The chief problem with all statistically derived formulas is that in order to be widely applicable, they must be based on a broad sample of individuals.

Yet, that breadth makes them inherently inaccurate. The ideal statistical estimation method for an individual is based on a sample of similar individuals. For instance, a skinfold based body density formula developed from a sample of male collegiate rowers is likely to be much more accurate for estimating the body density of a male collegiate rower than a method developed using a sample of the general population, because the sample is narrowed down by age, sex, physical fitness level, type of sport, and lifestyle factors.

On the other hand, such a formula is unsuitable for general use. The skinfold estimation methods are based on a skinfold test , also known as a pinch test , whereby a pinch of skin is precisely measured by calipers , also known as a plicometer , [19] at several standardized points on the body to determine the subcutaneous fat layer thickness.

Some formulas require as few as three measurements, others as many as seven. The accuracy of these estimates is more dependent on a person's unique body fat distribution than on the number of sites measured.

As well, it is of utmost importance to test in a precise location with a fixed pressure. Although it may not give an accurate reading of real body fat percentage, it is a reliable measure of body composition change over a period of time, provided the test is carried out by the same person with the same technique.

Skinfold-based body fat estimation is sensitive to the type of caliper used, and technique. This method also only measures one type of fat: subcutaneous adipose tissue fat under the skin.

Two individuals might have nearly identical measurements at all of the skin fold sites, yet differ greatly in their body fat levels due to differences in other body fat deposits such as visceral adipose tissue: fat in the abdominal cavity.

Some models partially address this problem by including age as a variable in the statistics and the resulting formula.

Older individuals are found to have a lower body density for the same skinfold measurements , which is assumed to signify a higher body fat percentage. However, older, highly athletic individuals might not fit this assumption, causing the formulas to underestimate their body density.

Ultrasound is used extensively to measure tissue structure and has proven to be an accurate technique to measure subcutaneous fat thickness. By making thickness measurements at multiple sites on the body you can calculate the estimated body fat percentage. Ultrasound equipment is expensive, and not cost-effective solely for body fat measurement, but where equipment is available, as in hospitals, the extra cost for the capability to measure body fat is minimal.

There also exist formulas for estimating body fat percentage from an individual's weight and girth measurements. For example, the U. Navy circumference method compares abdomen or waist and hips measurements to neck measurement and height and other sites claim to estimate one's body fat percentage by a conversion from the body mass index.

In the U. Navy, the method is known as the "rope and choke. The U. Army and U. Marine Corps also rely on the height and circumference method. Females are measured around the hips, waist, and neck. These measurements are then looked up in published tables, with the individual's height as an additional parameter.

This method is used because it is a cheap and convenient way to implement a body fat test throughout an entire service. Methods using circumference have little acceptance outside the Department of Defense due to their negative reputation in comparison to other methods.

The method's accuracy becomes an issue when comparing people with different body compositions, those with larger necks artificially generate lower body fat percentage calculations than those with smaller necks.

Body fat can be estimated from body mass index BMI , a person's mass in kilograms divided by the square of the height in meters; if weight is measured in pounds and height in inches, the result can be converted to BMI by multiplying by These formulae are based on work by researchers published in peer-reviewed journals, but their correlation with body fat are only estimates; body fat cannot be deduced accurately from BMI.

Body fat may be estimated from the body mass index by formulae derived by Deurenberg and co-workers. Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. However — contrary to the aforementioned internal and external cross-validation —, these formulae definitely proved unusable at least for adults and are presented here illustratively only.

Still, the following formula designed for adults proved to be much more accurate at least for adults: [28]. Other indices may be used; the body adiposity index was said by its developers to give a direct estimate of body fat percentage, but statistical studies found this not to be so.

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Medical concepts. The Hospital Authority of Hong Kong recommends the use of the following BMI ranges: [19]. A study from the Japan Society for the Study of Obesity JASSO presents the following table of BMI categories: [20] [21] [22].

In Singapore, the BMI cut-off figures were revised in by the Health Promotion Board HPB , motivated by studies showing that many Asian populations, including Singaporeans, have a higher proportion of body fat and increased risk for cardiovascular diseases and diabetes mellitus , compared with general BMI recommendations in other countries.

The BMI cut-offs are presented with an emphasis on health risk rather than weight. In the UK, NICE guidance recommends prevention of type 2 diabetes should start at a BMI of 30 in White and New research based on a large sample of almost 1.

In , the U. National Institutes of Health brought U. This had the effect of redefining approximately 25 million Americans, previously healthy , to overweight. This can partially explain the increase in the overweight diagnosis in the past 20 years [ when?

By , National Health and Nutrition Examination Survey of showed that The BMI ranges are based on the relationship between body weight and disease and death. The BMI is generally used as a means of correlation between groups related by general mass and can serve as a vague means of estimating adiposity.

The duality of the BMI is that, while it is easy to use as a general calculation, it is limited as to how accurate and pertinent the data obtained from it can be. Generally, the index is suitable for recognizing trends within sedentary or overweight individuals because there is a smaller margin of error.

This general correlation is particularly useful for consensus data regarding obesity or various other conditions because it can be used to build a semi-accurate representation from which a solution can be stipulated, or the RDA for a group can be calculated.

Similarly, this is becoming more and more pertinent to the growth of children, since the majority of children are sedentary. Smaller effects are seen in prospective cohort studies which lend to support active mobility as a means to prevent a further increase in BMI.

In France, Italy, and Spain, legislation has been introduced banning the usage of fashion show models having a BMI below A study published by Journal of the American Medical Association JAMA in showed that overweight people had a death rate similar to normal weight people as defined by BMI, while underweight and obese people had a higher death rate.

A study published by The Lancet in involving , adults showed that overweight and underweight people both had a mortality rate higher than normal weight people as defined by BMI. The optimal BMI was found to be in the range of High BMI is associated with type 2 diabetes only in people with high serum gamma-glutamyl transpeptidase.

In an analysis of 40 studies involving , people, patients with coronary artery disease with normal BMIs were at higher risk of death from cardiovascular disease than people whose BMIs put them in the overweight range BMI 25— One study found that BMI had a good general correlation with body fat percentage, and noted that obesity has overtaken smoking as the world's number one cause of death.

A study that followed 11, subjects for up to eight years concluded that BMI is not the most appropriate measure for the risk of heart attack, stroke or death. A better measure was found to be the waist-to-height ratio. The medical establishment [50] and statistical community [51] have both highlighted the limitations of BMI.

Part of the statistical limitations of the BMI scale is the result of Quetelet's original sampling methods. For women, and people of non-European origin, the scale is often biased. As noted by sociologist Sabrina Strings, the BMI is largely inaccurate for black people especially, disproportionately labelling them as overweight even for healthy individuals.

The exponent in the denominator of the formula for BMI is arbitrary. The BMI depends upon weight and the square of height. Since mass increases to the third power of linear dimensions, taller individuals with exactly the same body shape and relative composition have a larger BMI.

So, if all body dimensions double, and mass scales naturally with the cube of the height, then BMI doubles instead of remaining the same. This results in taller people having a reported BMI that is uncharacteristically high, compared to their actual body fat levels.

In comparison, the Ponderal index is based on the natural scaling of mass with the third power of the height. However, many taller people are not just "scaled up" short people but tend to have narrower frames in proportion to their height.

tables are excellent for identifying obesity and body fat in large populations, but they are far less reliable for determining fatness in individuals. For US adults, exponent estimates range from 1. In other words, people with small frames would be carrying more fat than optimal, but their BMI indicates that they are normal.

Conversely, large framed or tall individuals may be quite healthy, with a fairly low body fat percentage , but be classified as overweight by BMI. However, falling into one's ideal weight range for height and build is still not as accurate in determining health risk factors as waist-to-height ratio and actual body fat percentage.

Accurate frame size calculators use several measurements wrist circumference, elbow width, neck circumference, and others to determine what category an individual falls into for a given height. In this situation, BMI will increase without any corresponding increase in weight. Assumptions about the distribution between muscle mass and fat mass are inexact.

BMI generally overestimates adiposity on those with leaner body mass e. A study in June by Romero-Corral et al. In other words, the BMI will be mostly correct when determining a person to be obese, but can err quite frequently when determining a person not to be.

Despite this undercounting of obesity by BMI, BMI values in the intermediate BMI range of 20—30 were found to be associated with a wide range of body fat percentages. Body composition for athletes is often better calculated using measures of body fat, as determined by such techniques as skinfold measurements or underwater weighing and the limitations of manual measurement have also led to new, alternative methods to measure obesity, such as the body volume indicator.

It is not clear where on the BMI scale the threshold for overweight and obese should be set. Because of this, the standards have varied over the past few decades. Between and the U. Dietary Guidelines have defined overweight at a variety of levels ranging from a BMI of In the National Institutes of Health NIH consensus conference recommended that overweight BMI be set at a BMI of In , an NIH report concluded that a BMI over 25 is overweight and a BMI over 30 is obese.

This became the definitive guide for determining if someone is overweight. One study found that the vast majority of people labelled 'overweight' and 'obese' according to current definitions do not in fact face any meaningful increased risk for early death.

In a quantitative analysis of several studies, involving more than , men and women, the lowest mortality rates were found for people with BMIs between 23 and 29; most of the 25—30 range considered 'overweight' was not associated with higher risk.

The corpulence index uses an exponent of 3 rather than 2. The corpulence index yields valid results even for very short and very tall people, [63] which is a problem with BMI. For example, a In general, we do not err much when we assume that during development the squares of the weight at different ages are as the fifth powers of the height.

This exponent of 2. The scaling factor of 1. In Trefethen's analysis, an exponent of 2. BMI Prime is a dimensionless number independent of units. Individuals with BMI Prime less than 0. BMI Prime is useful clinically because it shows by what ratio e.

In South East Asian and South Chinese populations see § international variations , BMI Prime should be calculated using an upper limit BMI of 23 in the denominator instead of BMI Prime allows easy comparison between populations whose upper-limit optimal BMI values differ.

Waist circumference is a good indicator of visceral fat , which poses more health risks than fat elsewhere. According to the U. National Institutes of Health NIH , waist circumference in excess of 1, mm 40 in for men and mm 35 in for non-pregnant women is considered to imply a high risk for type 2 diabetes, dyslipidemia , hypertension , and cardiovascular disease CVD.

Waist circumference can be a better indicator of obesity-related disease risk than BMI. For example, this is the case in populations of Asian descent and older people. Waist-to-hip circumference ratio has also been used, but has been found to be no better than waist circumference alone, and more complicated to measure.

A related indicator is waist circumference divided by height. The values indicating increased risk are: greater than 0. The Surface-based Body Shape Index SBSI is far more rigorous and is based upon four key measurements: the body surface area BSA , vertical trunk circumference VTC , waist circumference WC and height H.

Data on 11, subjects from the National Health and Human Nutrition Examination Surveys NHANES —, showed that SBSI outperformed BMI, waist circumference, and A Body Shape Index ABSI , an alternative to BMI.

Within some medical contexts, such as familial amyloid polyneuropathy , serum albumin is factored in to produce a modified body mass index mBMI.

The mBMI can be obtained by multiplying the BMI by serum albumin , in grams per litre.

Which remains a practical and widely used tool for population health and screening and is used daily in clinical practice. Its relationship with body composition per se is controversial.

It is easy to use, reproducible, and trackable but is unable to distinguish between fat and lean masses. It is important to remember and explain to our patients that BMI can be utilized as a part of a comprehensive health assessment rather than the sole determinant of obesity or body fat percentage.

Another commonly utilized and simple measurement is Waist circumference WC. It has long been recognized in adults that waist—hip ratio is independently associated with morbidity after adjustment for relative weight, such that the use of relative weight and body shape simultaneously gives a better estimate of the risk of morbidity than either alone Rimm There are limitations including inter-user variability something we have encountered in our office.

In summary, BMI and DXA serve different purposes in body composition assessment. BMI is a practical and widely used tool for population health and screening, while DXA scanning offers a more detailed and accurate evaluation of body composition in clinical and research settings. The choice between the two methods depends on the specific goals of the assessment and the level of precision required for the given context.

Chair of the Department of Obstetrics and Gynecology at SVMC, Chair of the Vermont Section of ACOG, and Clinical Assistant Professor in OBGYN, Geisel School of Medicine at Dartmouth.

Member of the OMA Outreach and Advocacy Committees. What is the Gold Standard for determining Body Fat? August 8, What is the Gold Standard for determining Body Fat?

Share this post. It still has some limitations: Regional Fat Distribution DXA provides an overall body fat percentage and differentiates between fat and lean mass. It may not distinguish between visceral fat deep abdominal fat and subcutaneous fat fat under the skin , which can be relevant for assessing health risks associated with central adiposity and fat accumulation.

Bone and Lean Mass Influence Measures the attenuation of X-rays passing through the body, and both bone mineral content and lean mass can contribute to this measurement.

One of the major sources of cholesterol in the diet is animal products. Many fresh meats, poultry and fish do not have a nutrition facts label. The average cholesterol per ounce of an animal product is 25 mg. Divide the calories from fat by the total calories.

Keep in mind not every food you eat needs to contain less than 30 percent of the calories from fat. Some foods will contain no fat, such as fruit, and others may contain a higher percentage. It's the average of all the foods in your diet that you want to keep to less than 30 percent.

Too much sodium in your diet can contribute to high blood pressure, a major risk factor for heart disease and stroke. Kidney disease and osteoporosis are also associated with a high sodium diet. The average American eats 5,, mg.

of sodium per day. Most of this comes from processed foods. Our bodies need about mg. per day to function. You can reduce the sodium in your diet a lot by eating fresh foods rather than foods in bags, boxes and cans. Most government and health organizations suggest a limit of 1,, mg. When it comes to sodium, less is best.

Carbohydrates are the main source of energy during most physical activity. Carbohydrates should comprise percent of your calories, or about grams per day depending on your caloric requirement.

Fiber may play as much of a role in disease prevention as fat. Aim for at least 30 grams per day. Soluble fiber is especially helpful for lowering LDL cholesterol.

Compare fiber grams on breads, cereals, crackers, etc. High fiber foods contain at least 3 grams of fiber per serving. Don't worry if there is a little more fat in the high-fiber foods because the wheat germ of whole grain products contains some unsaturated fat.

Sugar is present in many processed foods; some is naturally occurring and some is added. Your body doesn't know the difference, so the total sugar content is the amount listed on the nutrition facts.

Your sugar intake should not be more than 10 percent of your total calories. HFCS is frequently used in processed foods to give sweetness. Unfortunately, it can raise LDL cholesterol if consumed in large amounts. Look for it in the ingredients. Try to avoid consuming a lot of foods with HFCS.

The scan compares the amount of fat around the belly known as android fat to the amount of fat around the hips and thighs known as gynoid fat , spitting out a ratio. Visceral fat — fat stored deep in the belly, around the organs — is associated with a number of health consequences , including Type 2 diabetes and heart disease.

While visceral fat carries risks, fat stored around the legs may actually be protective against metabolic disease, Visaria said. Although there are no set guidelines for obesity cutoffs using this measurement, he said, the general rule of thumb is that anything over 1.

Despite BMI being an imperfect tool, Almandoz said, it should not be completely thrown out. Any measurement of body composition needs to be able to connect results, whether that be the amount of fat a person has or where that fat sits, to specific health risks, he said.

Jack Resneck Jr. Kaitlin Sullivan is a contributor for NBCNews. com who has worked with NBC News Investigations.

She reports on health, science and the environment and is a graduate of the Craig Newmark Graduate School of Journalism at City University of New York. IE 11 is not supported. For an optimal experience visit our site on another browser.

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