- About Adult BMI
- What is BMI?
- How is BMI used?
- What are the BMI trends for adults in the United States?
- Why is BMI used to measure overweight and obesity?
- What are some of the other ways to assess excess body fatness besides BMI?
- How is BMI calculated?
- How is BMI interpreted for adults?
- Is BMI interpreted the same way for children and teens as it is for adults?
- How good is BMI as an indicator of body fatness?
- If an athlete or other person with a lot of muscle has a BMI over 25, is that person still considered to be overweight?
- What are the health consequences of obesity for adults?
- Is Body Mass Index reliable?
- Alternative estimates of weight-related health risks
- Body Mass Index (BMI)
- What’s your Body Mass Index?
- Body mass index – BMI
- Calculate BMI
- Body Mass Index (BMI) – The Complete Guide
- 1. What is the Body Mass Index (BMI)?
- 2. What is the Body Mass Index Used for?
- 3. Global Body Mass Index Statistics vs. USA
- 4. Possible Limitations of the BMI
- 5. Alternative Measures to BMI
- 6. The Benefits of Keeping a Healthy Weight
- 7. Body Mass Index – The Final Word
About Adult BMI
What is BMI?
BMI is a person’s weight in kilograms divided by the square of height in meters. BMI does not measure body fat directly, but research has shown that BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods 1,2,3. Furthermore, BMI appears to be as strongly correlated with various metabolic and disease outcome as are these more direct measures of body fatness 4,5,6,7,8,9. In general, BMI is an inexpensive and easy-to-perform method of screening for weight category, for example underweight, normal or healthy weight, overweight, and obesity.
How is BMI used?
A high BMI can be an indicator of high body fatness. BMI can be used as a screening tool but is not diagnostic of the body fatness or health of an individual.
To determine if a high BMI is a health risk, a healthcare provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings10.
What are the BMI trends for adults in the United States?
The prevalence of adult BMI greater than or equal to 30 kg/m2 (obese status) has greatly increased since the 1970s. Recently, however, this trend has leveled off, except for older women. Obesity has continued to increase in adult women who are age 60 years and older.
To learn more about the trends of adult obesity, visit Adult Obesity Facts.
Why is BMI used to measure overweight and obesity?
BMI can be used for population assessment of overweight and obesity. Because calculation requires only height and weight, it is inexpensive and easy to use for clinicians and for the general public. BMI can be used as a screening tool for body fatness but is not diagnostic.
To see the formula based on either kilograms and meters or pounds and inches, visit How is BMI calculated?
What are some of the other ways to assess excess body fatness besides BMI?
Other methods to measure body fatness include skinfold thickness measurements (with calipers), underwater weighing, bioelectrical impedance, dual-energy x-ray absorptiometry (DXA), and isotope dilution 1,2,3. However, these methods are not always readily available, and they are either expensive or need to be conducted by highly trained personnel. Furthermore, many of these methods can be difficult to standardize across observers or machines, complicating comparisons across studies and time periods.
How is BMI calculated?
BMI is calculated the same way for both adults and children. The calculation is based on the following formulas:
|Measurement Units||Formula and Calculation|
|Kilograms and meters (or centimeters)||Formula: weight (kg) / 2
With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Because height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters.
Example: Weight = 68 kg, Height = 165 cm (1.65 m)
|Pounds and inches||Formula: weight (lb) / 2 x 703
Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703.
Example: Weight = 150 lbs, Height = 5’5″ (65″)
How is BMI interpreted for adults?
For adults 20 years old and older, BMI is interpreted using standard weight status categories. These categories are the same for men and women of all body types and ages.
The standard weight status categories associated with BMI ranges for adults are shown in the following table.
|18.5 – 24.9||Normal or Healthy Weight|
|25.0 – 29.9||Overweight|
|30.0 and Above||Obese|
For example, here are the weight ranges, the corresponding BMI ranges, and the weight status categories for a person who is 5′ 9″.
|Height||Weight Range||BMI||Weight Status|
|5′ 9″||124 lbs or less||Below 18.5||Underweight|
|125 lbs to 168 lbs||18.5 to 24.9||Normal or Healthy Weight|
|169 lbs to 202 lbs||25.0 to 29.9||Overweight|
|203 lbs or more||30 or higher||Obese|
For children and teens, the interpretation of BMI depends upon age and sex. For more information about interpretation for children and teens, read – What is a BMI percentile and how is it interpreted?
Is BMI interpreted the same way for children and teens as it is for adults?
BMI is interpreted differently for children and teens, even though it is calculated using the same formula as adult BMI. Children and teen’s BMI need to be age and sex-specific because the amount of body fat changes with age and the amount of body fat differs between girls and boys. The CDC BMI-for-age growth charts take into account these differences and visually show BMI as a percentile ranking. These percentiles were determined using representative data of the U.S. population of 2- to 19-year-olds that was collected in various surveys from 1963-65 to 1988-9411.
Obesity among 2- to 19-year-olds is defined as a BMI at or above the 95th percentile of children of the same age and sex in this 1963 to 1994 reference population. For example, a 10-year-old boy of average height (56 inches) who weighs 102 pounds would have a BMI of 22.9 kg/m2. This would place the boy in the 95th percentile for BMI – meaning that his BMI is greater than that of 95% of similarly aged boys in this reference population – and he would be considered to have obesity.
For more information and to access the CDC Growth Charts
For adults, the interpretation of BMI does not depend on sex or age. Read more about interpreting adult BMI.
How good is BMI as an indicator of body fatness?
The correlation between the BMI and body fatness is fairly strong1,2,3,7, but even if 2 people have the same BMI, their level of body fatness may differ12.
- At the same BMI, women tend to have more body fat than men.
- At the same BMI, Blacks have less body fat than do Whites13,14, and Asians have more body fat than do Whites15
- At the same BMI, older people, on average, tend to have more body fat than younger adults.
- At the same BMI, athletes have less body fat than do non-athletes.
The accuracy of BMI as an indicator of body fatness also appears to be higher in persons with higher levels of BMI and body fatness16. While, a person with a very high BMI (e.g., 35 kg/m2) is very likely to have high body fat, a relatively high BMI can be the results of either high body fat or high lean body mass (muscle and bone). A trained healthcare provider should perform appropriate health assessments in order to evaluate an individual’s health status and risks.
If an athlete or other person with a lot of muscle has a BMI over 25, is that person still considered to be overweight?
According to the BMI weight status categories, anyone with a BMI between 25 and 29.9 would be classified as overweight and anyone with a BMI over 30 would be classified as obese.
However, athletes may have a high BMI because of increased muscularity rather than increased body fatness. In general, a person who has a high BMI is likely to have body fatness and would be considered to be overweight or obese, but this may not apply to athletes. A trained healthcare provider should perform appropriate health assessments in order to evaluate an individual’s health status and risks.
What are the health consequences of obesity for adults?
People who have obesity are at increased risk for many diseases and health conditions, including the following: 10, 17, 18
- All-causes of death (mortality)
- High blood pressure (Hypertension)
- High LDL cholesterol, low HDL cholesterol, or high levels of triglycerides (Dyslipidemia)
- Type 2 diabetes
- Coronary heart disease
- Gallbladder disease
- Osteoarthritis (a breakdown of cartilage and bone within a joint)
- Sleep apnea and breathing problems
- Chronic inflammation and increased oxidative stress19,20
- Some cancers (endometrial, breast, colon, kidney, gallbladder, and liver)
- Low quality of life
- Mental illness such as clinical depression, anxiety, and other mental disorders21,22
- Body pain and difficulty with physical functioning23
For more information about these and other health problems associated with obesity, visit Health Effects
This calculator should only be used by adults (pregnant or lactating women should not rely on these BMI readings), and no action should be taken based on its values other than to consult a suitably qualified person such as a doctor.
The calculator will give you an idea of how your weight compares to common values. Body Mass Index (or BMI) is calculated as your weight (in kilograms) divided by the square of your height (in metres) or BMI = Kg/M2.
Is Body Mass Index reliable?
Your BMI, or Body Mass Index, is a measure of your weight compared to your height. Accurate assessments of obesity are important, as being overweight or obese significantly increases your risk of a variety of medical conditions including type 2 diabetes, heart disease and cancer. As levels of overweight or obesity increase, the spotlight has fallen on BMI and its shortcomings as a measure of ideal weight for individuals, rather than whole populations of people where ‘averages’ apply.
“Some people naturally have a larger frame than others. But this causes quite a small variation in weight and is accounted for in the range of healthy BMI. There is really no such thing as someone who is big-boned.” Dr Jan Sambrook, How to lose weight in a healthy way
For most adults, BMI gives a good estimate of your weight-related health risks. If your BMI is over 35, your weight is definitely putting your health at risk, regardless of the factors below. However, there are some situations where BMI may underestimate or overestimate these risks in the 25-35 BMI range. The main ones are:
Your GP or health visitor can advise on where your child sits on the ‘centile charts’ used to estimate healthy weights for children.
Usual BMI estimates do not apply if you’re pregnant.
If you are very muscular
BMI assumes you have an average amount of body fat, including ‘intra-abdominal fat’ – fat deep inside your stomach cavity rather than under your skin. Intra-abdominal fat is much more closely linked to risks of type 2 diabetes and heart disease than fat under the skin.
If you are very muscular, your level of body fat may be lower than predicted by your BMI. However, this only applies to people who do high levels of exercise – much more than average.
If you are of Asian origin
People of Asian origin are prone to accumulating intra-abdominal fat (fat deep inside your stomach cavity rather than under your skin) at a lower BMI than people of Caucasian origin. People with this pattern of weight gain are described as ‘apples’ rather than ‘pears’ from their body outline. This means their health risks start to rise at a lower BMI, because intra-abdominal fat is directly linked to development of heart disease and type 2 diabetes.
The World Health Organisation has looked at the evidence and because of the variability between different Asian populations, it hasn’t officially changed the cut-off points. However, it does recommend that for public health purposes, some Asian groups should be considered overweight if their BMI is 22-25, and obese with a BMI of 26-31.
Older people (over 65, possibly over 60)
Because muscle mass tends to drop and body fat tends to rise in older people, BMI may not be an accurate reflector of body fat if you’re over 60.
If you feel BMI may not accurately reflect whether you are overweight or obese, measuring your abdominal circumference, waist-hip or waist-height ratio may give you a more realistic estimate.
You measure your waist circumference half way between the bottom of your ribcage and the top of your hip bones, with the tape measure parallel to the floor. You must be breathing out when you measure.
- Increased health risk – ≥94cm
- High health risk – ≥102cm
- Increased health risk – ≥80cm
- High health risk – ≥88cm
Waist to hip ratio
To check your waist to hip ratio, measure your waist circumference (as above), and your hip size at the widest part of your hips. Divide your abdominal circumference by your hip measurement to give a ratio.
- In women, a waist to hip ratio greater than 0.85 is associated with greater than average risk.
- In men, a waist to hip ratio greater than 1.00 is associated with greater than average risk.
Waist to height ratio
A recent study comparing BMI, waist circumference, waist to hip ratio and waist to height ratio found that the most accurate way of predicting your whole-body fat level was waist-height ratio.
Measure your waist circumference as above and simply divide it by your height – fairly obviously both measurements should either be in imperial (inches) or metric (cm).
Whole body obesity is defined by a waist-height ratio of:
- 0.53 or more for men
- 0.54 or more for women
Abdominal obesity was defined by a waist-height ratio of 0.59 or more.
Q: What is a healthy BMI range? And what does that actually mean?
A: BMI stands for body mass index. We take a person’s weight and height and convert that into metric units, and then calculate weight per meter of body surface area – so it’s measured in kilograms per meters squared. This is used as an approximation of body composition, in particular the amount of total body fat.
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It’s easy because we can measure your height and your weight and we can calculate this BMI, which standardizes weight across heights for adults. The BMI scale for adults is:
- Under 18: Underweight
- 18-25: Normal
- >25-30: Overweight
- >30-40: Obese
- Above 40: Morbidly obese
However, BMI is only an estimation of body composition. So there are people who carry a lot of muscle mass whose BMI will be high because they weigh more, and it’s not really a good indication of what their body mass is. But for the vast majority of Americans, it’s a good rough estimate.
There’s an interesting paper that was published in The Lancet in August 2016 that combined the data from 239 clinical trials and found that, in people who never smoke cigarettes, increasing BMI was associated with all causes of mortality. So higher BMI is associated with increased risk for cancer, heart disease and stroke.
But there are other measurements that can help determine whether you’re at a healthy body weight. One that we probably don’t use enough is waist circumference. If you start an exercise program or a diet and you’re losing inches around your midsection, even if the scale doesn’t change a whole lot, that’s still a good sign.
— Family medicine physician Robert Bales, MD, MPH, FAAFP
Body Mass Index (BMI)
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What Is BMI?
Body mass index (BMI) is a calculation that uses height and weight to estimate how much body fat someone has. You can use the KidsHealth BMI calculator below to find your child’s BMI. But it’s also important to talk to your child’s doctor to help understand the results.
Starting when your child is 2 years old, the doctor will determine BMI at all routine checkups. Because BMI changes with age, doctors plot children’s BMI measurements on standard gender-specific growth charts. Over several visits, the doctor is able to track your child’s growth pattern.
Although not a perfect measure of body fat, BMI helps identify children who are gaining weight too slowly or too quickly.
What Do the Figures Mean?
BMI percentiles show how a child’s measurements compare with others the same gender and age. For example, if a child has a BMI in the 60th percentile, 60% of the kids of the same gender and age who were measured had a lower BMI.
BMI is not a direct measure of body fat. Kids can have a high BMI if they have a large frame or a lot of muscle, not excess fat. And a kid with a small frame may have a normal BMI but still can have too much body fat.
BMI is less accurate during puberty. It’s common for kids to gain weight quickly — and see their BMI go up — during puberty. Your doctor can help you figure out whether this weight gain is a normal part of development or whether it’s something to be concerned about.
The categories that describe a person’s weight are:
- Underweight: BMI is below the 5th percentile age, gender, and height.
- Healthy weight: BMI is equal to or greater than the 5th percentile and less than the 85th percentile for age, gender, and height.
- Overweight: BMI is at or above the 85th percentile but less than the 95th percentile for age, gender, and height.
- Obese: BMI is at or above the 95th percentile for age, gender, and height.
It’s important to look at the BMI as a trend instead of focusing on individual numbers. Any one measurement, taken out of context, can give you the wrong impression of your child’s growth.
While BMI is an important indicator of healthy growth and development, BMI is not a perfect measure of body fat. If you’re concerned that your child may be gaining or losing weight too fast, talk to your doctor.
Reviewed by: Mary L. Gavin, MD Date reviewed: January 2020
What’s your Body Mass Index?
Your Body Mass Index (BMI) is a way of finding out if your weight is putting your health at risk and is used by health professionals around the world. It is based on your height and weight and can be worked out by taking your weight in kilograms and dividing it by your height (in metres) squared.
For any height there is a range of healthy weights. BMI is classified in the following way:
- A BMI of less than 18.5 kg/m2 indicates you are underweight. You may need to gain weight.
- If your BMI is 19 to 24.9 kg/m2, you’re are a healthy weight, and should aim to stay that way.
- A BMI of 25 to 29 kg/m2 is defined as overweight. It’s a good idea to lose some weight for your health’s sake, or at least aim to prevent further weight gain.
- A BMI of over 30 kg/m2 is defined as obese and means your health is at risk. Losing weight will improve your health.
Note: BMI is not always a good reflection of body fatness. A very muscular person might have a high BMI when in fact their body fat is at a healthy level, as muscle weighs more than fat.
You should visit your GP if you feel you need help to manage your weight and health.
Body mass index – BMI
BMI, formerly called the Quetelet index, is a measure for indicating nutritional status in adults. It is defined as a person’s weight in kilograms divided by the square of the person’s height in metres (kg/m2). For example, an adult who weighs 70 kg and whose height is 1.75 m will have a BMI of 22.9.
70 (kg)/1.752 (m2) = 22.9 BMI
For adults over 20 years old, BMI falls into one of the following categories.
Table 1. Nutritional status
Obesity class I
Obesity class II
Obesity class III
The BMI ranges are based on the effect excessive body fat has on disease and death and are reasonably well related to adiposity. BMI was developed as a risk indicator of disease; as BMI increases, so does the risk for some diseases. Some common conditions related to overweight and obesity include: premature death, cardiovascular diseases, high blood pressure, osteoarthritis, some cancers and diabetes.
BMI is also recommended for use in children and adolescents. In children, BMI is calculated as for adults and then compared with z-scores or percentiles. During childhood and adolescence the ratio between weight and height varies with sex and age, so the cut-off values that determine the nutritional status of those aged 0–19 years are gender- and age-specific. The cut-off points of the 2006 BMI-for-age reference for children aged 0–5 years for the diagnosis of overweight and obesity were set as the 97th and the 99th percentile, respectively. For those aged 5–19 years, overweight is defined as a BMI-for-age value over +1 SD and obesity as a BMI-for-age value over +2 SD.
BMI is very easy to measure and calculate and is therefore the most commonly used tool to correlate risk of health problems with the weight at population level. It was developed by Adolphe Quetelet during the 19th century. During the 1970s and based especially on the data and report from the Seven Countries study, researchers noticed that BMI appeared to be a good proxy for adiposity and overweight related problems.
Like any other measure it is not perfect because it is only dependant on height and weight and it does not take into consideration different levels of adiposity based on age, physical activity levels and sex. For this reason it is expected that it overestimates adiposity in some cases and underestimates it in others.
Other measures, such as waist circumference (WC), can complement BMI estimates. Association between WC and health risks is not an easy task and should be done scientifically using proper techniques.
Body Mass Index (BMI) – The Complete Guide
The most recent obesity statistics from the World Health Organization (WHO) make grim reading. The WHO published an updated list of statistics in February 2018 and found that global obesity has tripled since 1975. There are now 1.9 billion overweight adults around the world, 650 million of whom are obese.
The terms ‘overweight’ and ‘obese’ are defined as “abnormal or excessive fat accumulation that may impair health” by the WHO. In other words, aesthetics doesn’t enter the equation; carrying too much weight is bad for your health. There are numerous tools used to calculate whether or not a person is overweight. Even with the advances in medical technology, the Body Mass Index (BMI) is one of the most frequently used measurements of a person’s physical shape and general health, some 150 years after it was first conceived.
1. What is the Body Mass Index (BMI)?
The body mass index, occasionally called the Quetelet index, is a value taken from a person’s height and weight. It is also determined via a BMI chart table and is an attempt to quantify the level of tissue mass (comprised of bone, fat, and muscle) in a person.
The result is used to determine if that individual is obese, overweight, normal weight or underweight depending on where they fall within the BMI category ranges.
1.1 How is BMI Calculated?
The body mass index formula is easy to determine. It’s a simple calculation that takes into account your weight and height.
- The imperial BMI formula = Weight (LBS) x 703 ÷ Height (Inches²)
- The metric BMI formula = Weight (KG) ÷ Height (Metres²)
If you wish to calculate your BMI using the imperial system, here’s the height and weight conversion figures:
- 1 kilogram = 2.2 pounds
- 1 foot = 12 inches
- 1 inch = 2.54 centimetres
If you are 5ft 4 inches by the imperial system, you are 162.56cm or 1.63m (rounded up) by the metric system.
Example BMI Calculations
Example 1: This is how to calculate your body mass index score if you were to weigh 209 pounds and are 6 feet 2 inches tall.
- 209 pounds = 95 kilograms
- 6 feet 2 inches = 1.88m
- 1.88 x 1.88 = 3.53
- 95/3.53 = 26.91
The BMI Score in this case = 26.91.
Example 2: Some countries use an entirely different calculation to reach the same result.
Weight in pounds / your height in inches squared x 703
Using the same example as before, you calculate as follows:
- (209 / 74 x 74) x 703 = (209 / 5,476) x 703
The BMI Score in this case = 26.83.
Why the difference? Because there is a certain element of ‘rounding up’ or ‘rounding down’ involved e.g. 26.784 becomes 26.78 and so on.
But where does this place you on the BMI category chart? In the next section we cover the bmi categories and explain the classifications.
1.2 Body Mass Index Categories
Technically, the BMI scale will place you in one of six categories. The table below lists the BMI categories along with the BMI score associated with each category.
|Classification||Body Mass Index Score|
|Underweight||less than 18.5|
|Normal Weight||18.5 – 24.9|
|Overweight||25 – 29.9|
|Obesity (Class 1)||30 – 34.9|
|Obesity (Class 2)||35 – 39.9|
|Extreme Obesity (Class 3)||40+|
The following body mass index chart allows you to manually get your BMI score and includes a classification of the BMI category you reside within.
1.3 BMI for Children
Although the BMI calculator works in the same way for children, the measurement is used differently. While the BMI ranges remain the same for adults throughout their life, these figures change in children because kids are still growing and do so at different rates. As a result, BMI is a measure of weight for height compared to children of the same age. This calculation results in a body mass index percentile.
For instance, if your child is in the 50th percentile, it means that 50% of children of the same age have the same BMI figure or less. The 85th percentile means that 85% of kids have the same or lower BMI and this is a figure where your child is classified as being ‘at risk’ of becoming overweight. At the 95th percentile, your child is classified as ‘overweight’.
Example: If your child is a 14-year-old boy who is 5ft 3 inches tall and weighs 120 pounds for example, his BMI is 21.3 which puts him in the 76th percentile. This BMI figure indicates that he is at a healthy weight because the proper range is between 90 and 128 pounds in this instance.
Here is what that reading looks like when based on BMI percentiles.
1.4 BMI Charts
Body Mass Index charts are useful for visualizing the ranges associated with each BMI category. You can use them to easily locate your height and weight to determine your BMI score and the associated BMI category you fit within.
BMI Chart for Adults (Men & Women)
BMI Chart for Kids & Teens (Boys)
BMI Chart for Kids & Teens (Girls)
The Body Mass Index is sometimes called the Quetelet Index after its creator, a Belgian mathematician, astronomer, sociologist, statistician and all-around genius named Lambert Adolphe Jacques Quetelet. He came up with the idea sometime between 1830 and 1850 as part of his development of ‘social physics’.
Even so, it was seldom used and only started to become popular in the latter part of the 20th century. The term Body Mass Index was first coined by Ancel Keys and other authors of a paper published in the Journal of Chronic Diseases in July 1972. According to the paper, BMI was “at least as good as any other relative weight index as an indicator of relative obesity.” At least Keys acknowledged that it was “not fully satisfactory.”
Prior to the 1980s, physicians used weight for height tables which differed according to gender. It was during this decade that the BMI calculator became the international standard for obesity measurement. Once governments around the world began noting the obesity problem in society, and started launching healthier lifestyle initiatives, the public at large became aware of BMI.
Initially, the threshold for being overweight was 27.8 but it was lowered to 25 internationally. In 1998, the United States National Institutes of Health followed suit and also reduced the BMI figure. This move resulted in 30 million Americans becoming classified as overweight overnight!
2. What is the Body Mass Index Used for?
Even though the Body Mass Index is over 150 years old, major health authorities such as the CDC and NIH in the United States still believe it is a ‘fairly reliable indicator of body fatness for most people.’
2.1 Public Health Statistics
Even today, BMI is used as the official measure of national obesity rates. For instance, the European Union continues to use it as a yardstick for the obesity epidemic and also suggests that people with higher BMI are at greater risk of diseases such as hypertension, cancer, and cardiovascular disease.
According to the Harvard T.H. Chan School of Public Health, your risk of developing conditions such as type-2 diabetes increases progressively as your BMI rises above 21.
2.2 Weight Range Analysis
The BMI range is also considered to be an accurate measure of your weight range. Therefore, if you have a BMI of 27, you are considered overweight regardless of what you actually weigh and your body composition or gender is not taken into account.
2.3 Screening Tool for Weight Problems
If a physician calculates a higher than normal BMI, the next step is to see if you are at risk of certain health problems. In fact, the main purpose of BMI is to determine whether you’re likely to develop a serious medical problem later in life.
In France for example, BMI is used as a screening tool for child malnutrition. The CDC champions the BMI scale as an effective means of determining whether children and teenagers are underweight, overweight, or obese.
2.4 Fashion Industry
The fashion industry’s obsession with exceedingly thin models has ensured that the BMI calculator has a permanent home there. The industry is constantly under fire for forcing women, in particular, to attain what the UK Women’s Equality Party calls “an unattainable level of thinness in women.” The party has called on all models with a BMI below 18.5 to be seen by a physician from an accredited list who will decide if that woman is healthy enough to work.
There is a law to that effect in Israel where male and female models with a BMI under 18.5 much obtain a medical certificate confirming a ‘normal’ BMI reading. For reference, Kate Moss, one of the most famous models ever, had a BMI of just 15 at the height of her fame. By any measure, including BMI, she was severely thin.
3. Global Body Mass Index Statistics vs. USA
BMI measurements vary around the globe and some nations have a greater ‘obesity’ problems than others according to the BMI scales. For a better understanding of global BMI scores, we have compiled statistics from six regions globally. First of all, here is the average body mass of people in different continents expressed in kilograms:
|Region||Average Body Mass (KGs)|
|Latin America / Caribbean||67.9 kg|
|North America||80.7 kg|
|Global Average||62.0 kg|
As you can see, Asians are significantly lighter than Americans for example and while they are shorter on average, it is evident that residents in North America have a higher BMI figure.
3.1 BMI Statistics in USA
The United States has the 2nd highest BMI average in the world behind Kuwait. America’s 28.8 average is just behind Kuwait’s 29.5 and speaks to a major problem in American society.
3.2 Average BMI of American Males
American males have the second highest average BMI on the planet with 28.5, slightly behind surprise entry, Argentina, which is #1 at 28.7.
3.3 Average BMI of American Females
The average BMI of females in the United States is even higher than in makes at 29.0 although disturbingly, there are several nations with higher averages including Kuwait, Trinidad and Tobago, and Egypt.
3.4 Obesity Rates in the USA
Estimates for obesity in the United States varies but according to World Obesity (from where we have gleaned obesity statistics from every country on the list), 41.5% of women aged 20+ were obese, the figure falls slightly to 37.9% in adult males.
4. Possible Limitations of the BMI
The Body Mass Index has its fair share of detractors. It has been derided as a flawed measurement tool. The following 4 points are often highlighted.
4.1 Age & Sex
There is a significant difference in body composition between the sexes and this isn’t taken into account by BMI calculators. Male BMI and female BMI measurements should be different because women tend to have a higher percentage of body fat. While men have little more than 2-5% essential body fat, women have 10-13%. Therefore, if a male and a female both have a BMI of 28, they are not equally overweight.
It is sadly also a fact that we lose muscle mass as we get older. Therefore, if you have the same BMI of 23 at age 65 as you did when you were 35, it doesn’t mean you are at a ‘healthy’ weight. You almost certainly have more body fat at 65 so you’re more likely to be overweight.
4.2 Physical Characteristics
The BMI calculator also exaggerates obesity in taller people and thinness in shorter people. For example, a two-meter tall man who weighs 104 kilograms is classified as ‘overweight’ according to the BMI scale (104 / 4 = 26).
In contrast, someone who is 1.5m tall and weighs 54 kilograms has a BMI of 24 (54 / 2.25) and is classified as ‘normal’ weight even though they are possibly overweight in real terms.
The fact of the matter is this: There were no calculators or computers during the 19th century so Ouetelet devised a system limited by the age he lived in. It is remarkable that over 150 years later, with so much technology at our fingertips, that medical professionals still use such an outdated system.
4.3 Weight vs. Body Fat
It is likely that BMI underestimates obesity, especially in the United States. In America, around one-third of the population are obese by BMI standards but other measurements suggest the true figure is closer to 60%.
Research conducted by Tomiyama et al. and published in the International Journal of Obesity in 2015, looked at the misclassification of cardiometabolic health when using BMI as a measuring stick. The team analyzed a group of participants over a seven-year period and made some startling discoveries. They found that 54 million Americans had been classified as obese or overweight through the Body Mass Index but cardiometabolic measurements showed them to be healthy. Meanwhile, 21 million people were deemed ‘normal’ in BMI terms but were actually unhealthy.
The fact that BMI uses your weight as its primary measuring tool means it is inaccurate. The density of your bone structure alone will throw off BMI calculations so a big-boned individual could wrongly be told that they are obese and at greater risk of medical conditions such as diabetes and stroke.
4.4 Athletes & Sports Professionals
BMI is usually NOT used for bodybuilders, sprinters, long distance runners or anyone else classified as a professional athlete or sportsperson. That’s because these individuals tend to have a higher rate of muscle mass which skews the figures. In the case of endurance athletes, a lack of muscle mass can also produce misleading results.
A prime example would be an Olympic sprinter who could have a BMI of 27; the same as an unfit couch potato. According to the BMI scale, both individuals are overweight even though one is a world class athlete and the other is an extremely unhealthy sedentary person.
5. Alternative Measures to BMI
5.1 Body Fat Percentage
A person’s body fat percentage is considered by some to be a better representation of their overall health than the BMI scale. It is simply a measurement of how much fat you’re carrying.
Example: a 180-pound male with 36 pounds of fat has a body fat percentage of 20%. Simply multiply the amount of fat you have by 100 and divide by your total weight:
36 x 100 = 3600
3600 / 180
Unlike the BMI scale, body fat percentage takes into account the differences between men and women. Here is the chart according to the American Council on Exercise:
As you can see, women tend to get 6-8% leeway on account of holding that much extra in essential fat. The Jackson and Pollock formula uses body fat percentage chart based on gender and age. For example, a 20-year-old male will ideally have 8.5% body fat but this figure rises to 20.9% aged 55.
There is special body fat percentage machines where you just stand on them and allow a mild electrical current to course through your body. You can also use the old-fashioned yet accurate calipers method. Simply measure the skin folds on specific points on the body to come up with a body fat % figure.
If you look at the charts above, you’ll see that a 27-year old woman with a calipers measurement of 12 millimeters is classified as ‘ideal’ with a body fat percentage of around 22-23%.
5.2 Waist to Hip Ratio
Other physicians believe that a person’s waist-to-hip ratio is an even better measure of health. According to a study published in PloS Magazine, waist circumstance is strongly linked to type 2 diabetes risk even after BMI is taken into account.
Researchers discovered that a non-obese but overweight man (in BMI terms) with a waist size of 102 cm or more (40.2 inches) has at least the same risk of type 2 diabetes as an obese male. The same situation applies to females with a waist size of 88 cm or more (34.6 inches).
Your waist-to-hip ratio is one of the best indicators of future disease risk because a higher ratio suggests that you have a high level of harmful visceral fat. This is the fat that accumulates around the internal organs and if you have too much of it, the result could be the release of hormones and proteins that lead to inflammation. This in turn damages arteries, enters your liver and impacts how the body breaks down fats and sugars.
Therefore, a man with 40-inch hips should ideally have a 32-inch waist (32 / 40 = 0.8).
A simpler version to judge your waist-to-height ratio is to keep your waist size to less than half of your height to reduce the risk of type 2 diabetes. Therefore, a 6-foot tall man (72 inches) should have a maximum waist measurement of 36 inches.
6. The Benefits of Keeping a Healthy Weight
6.1 Why Maintaining a Healthy Weight is Important
There is a lot more to keeping your weight in the ‘healthy’ range than merely looking good. It is a critical component of general health as it reduces your risk of developing serious medical conditions. If you’re overweight, it can be as simple as eating less and moving more. If you’re underweight, perhaps you should exercise less or eat a little more.
6.2 The Dangers of Being Overweight
Once you enter ‘overweight’ territory on the BMI scale, you will be at greater risk of a host of serious medical conditions.
In postmenopausal women, the risk of getting breast cancer increases by 20-40% when overweight according to a study by Munsell et al. published in 2014. Excess abdominal fat increases your risk by 43%.
Experts in the field suggest that a BMI of between 20 and 24 is the perfect zone for fertility. Up to 12% of fertility problems stem from weight problems (being overweight or underweight). In women, weight impacts periods and ovulation.
A study published in the Journal of the American College of Cardiology in April 2014 researched almost 15,000 Korean adults with no known case of heart disease. The team discovered that people with a BMI of over 25 were at greater risk of having early plaque buildup in their arteries than people at a ‘normal’ weight.
Type 2 Diabetes
According to WHO research entitled Global Report on Diabetes, up to 422 million adults were living with diabetes in 2014. This is almost quadruple the 1980 figure of 108 million. In that time, the rate of obesity has also risen. Recent research suggests that obesity accounts for up to 85% of the risk of developing type 2 diabetes. If you are obese, you are 80 times more likely to develop diabetes than someone with a BMI of 22 or less.
A 2012 study by the Johns Hopkins University School of Medicine showed a link between weight loss and better sleep. The six-month study was led by professor of medicine, Kerry Stewart, Ed. D, and involved 77 volunteers with pre-diabetes or type 2 diabetes. All 77 participants were either obese or overweight and were assigned to one of two groups. Group A went on a weight-loss diet and exercise regime. Group B only benefitted from the diet portion. Both groups lost 15 pounds and 15% of belly fat on average. What’s more, both groups improved their overall sleep score by 20%.
Reduced Life Expectancy
This is unquestionably the biggest danger of being overweight or obese. According to the Organization for Economic Co-operation and Development, your risk of death increases by 30% for every 33 pounds of excess weight you carry. A severely obese individual (someone with a BMI of 40+) can expect to live 8-10 years less than a person in the ‘normal’ BMI range.
6.3 The Dangers of Being Underweight
With such an emphasis on losing weight, it is easy to overlook the fact that being underweight also increases your risk of declining health. That’s one of the reasons why protest groups are so unhappy with the fashion industry. You fall into the ‘underweight’ category if your BMI is below 18.5.
According to the CDC, as at 2014, an estimated 1.4% of American adults are underweight. However, as this issue isn’t as well researched as obesity, there is a fairly high margin of error in the study. Here are some of the health risks associated with having an extremely low BMI score:
Contrary to what you may believe, malnutrition does not relate to eating or drinking too little. In reality, it is a term used to describe an insufficient intake of nutrients. If you don’t eat enough to fuel your body, symptoms can include fatigue and hair loss.
Decreased Immune Function
A review of the risk of infection in people with high and low BMI scores was published by Dobner and Kaser in January 2018. The review found that there was a notable connection between being underweight and increased infections. Malnourishment can reduce your immune system strength which means you’re less able to ward off infections and diseases.
A 2016 study by Lim and Park found that in premenopausal women, 24% of those with a BMI below 18.5 had low bone mass density. In contrast, only 9.4% of women with a BMI above 18.5 had the same issue.
Increase of Surgical Complications
In one study, underweight people who had total knee replacement surgery were at greater risk of infection afterward than people of a normal weight.
7. Body Mass Index – The Final Word
While it is true that there are a few concerns about BMI, it is still the most tried and trusted way to ascertain the average person’s general health. It is one of the quickest and easiest methods of determining whether you need to lose/gain weight and change your lifestyle. We recommend that you find out your BMI as soon as possible and if it is above or below the average range, book an appointment with your physician and seek advice. This simple test could prevent serious health issues going forward.
If your BMI is over 25 or below 18.5, you should conduct a body fat percentage test and also look at your waist-to-hip and waist-to-height ratios. A combination of all these measurements, plus an honest look in the mirror, should help you determine whether you need to lose or gain weight.
What isn’t in doubt is the growing levels of obesity around the world. The average BMI score of dozens of nations is in the overweight category and there are genuine fears that within a generation or two, there will be more obese people than non-obese.
It is a combination of longer working hours, easy access to cheap processed foods, and a lack of desire to exercise that is responsible for the current obesity epidemic. It would behoove nations in Europe, Oceania and North America, to look at the example set by countries in the Far East of Asia such as Japan which has an average BMI of 22.5, almost directly in the center of ‘normal’. Reduced consumption of processed foods and reliance on fresh fish, fruit, and vegetables ensures that Japan is one of the world’s healthiest nations.
For the record, there is unquestionably a link between BMI and wealth globally. Most of the countries with the lowest BMI averages are among the poorest on the planet. They include Bangladesh (20.2), Eritrea (20.2) and Ethiopia (20.3).
Meanwhile, several of the world’s wealthiest countries have the highest BMI averages. They include Kuwait (29.5), USA (28.8), and the United Arab Emirates (28). Unfortunately, when we revisit these statistics in a decade or so, the average BMI of most countries will have increased and at least one will enter the ‘Obese’ zone of 30 as an average.