What is the Ideal BMI for Men, Women and Children?
Body Mass Index or BMI is an easy to calculate method of determining your ideal weight. It requires only two values: your height and weight. You can calculate it on your own to understand which weight category you belong to.
Interpreting BMI in Adults and Children
The formula for arriving at a BMI measure for adults and children is the same, but there is a difference in the way it is interpreted.
If your BMI is below 18.5, you are underweight, and you need to talk to your doctor about gaining weight the healthy way. The ideal BMI for adults is between 18.5 and 24.9 and needs to be maintained by eating a balanced diet and adopting an active lifestyle.
However, if your BMI is above 25, you are overweight, and in case it is 30 or above, you have a serious problem at hand.
For children, anything between the 5th and 85th percentile is considered to be ideal.
Exceptions to BMI
While BMI is a valid measurement of body fat for both men and women, there are certain exceptions to this method:
- It does not reflect the true picture since it shows a higher count in people with muscular bodies, such as athletes, because it does not differentiate between fat and muscle.
- It underestimates body fat in the case of the elderly who have lost their muscle mass.
This means that BMI is not a fool proof way to determine one’s fat count, which is why doctors take into account other factors as well for determining obesity associated health risks.
BMI Statistics – United States
Almost 191 million adults in the USA are either overweight (BMI between 25 and 29) or obese (BMI of 30 and above). At the same time, less than 50% adults (approximately 68 million) have an ideal BMI of between 18.5 and 24.9.
The figures for women are also not very encouraging, and only 37 million women between the ages 20 and 74 have an ideal BMI.
Even more disturbing is the fact that the obesity epidemic has affected the younger generation as well, with 15% of all children and adolescents being overweight, and another 15% being at risk of becoming overweight in the future.
All You Want To Know About BMI for Women
BMI or Body Mass Index is the relationship between a person’s height and weight. BMI determines the amount of body fat, which in turn determines the degree of health risks. There is no separate BMI chart for women.
The mathematical formula used to calculate BMI takes into account the height and weight of an individual, but not the gender.
This means that the same chart applies to men, women, and children. However, BMI applies only to those who are at least 4 feet 10 inches (58 inches) tall and weigh at least 91 pounds.
If you want to know your BMI, you can do it in two ways:
- Refer to a BMI chart, which is a quick reference grid chart that shows your BMI against the appropriate height and weight. Those who are less than 58 inches tall or weigh less than 91 pounds need to use the BMI formula to gauge if they are healthy.
- You can use a BMI calculator to feed in your height and weight and find out your BMI. The universally accepted formula produces a unit of measure that is arrived upon by dividing your weight in kilograms by the square of your height in metres (kg/m2).
However, what is more important is the interpretation of BMI, which is an indication of where you stand as far as your weight is concerned:
- Underweight: BMI below 18.5
- Normal: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 to 29.9
- Obese: BMI 30.0 and above
Since there is no specific BMI chart for women, the above interpretation applies to all adults. Although BMI for children is calculated the same way as it is for adults, it is compared to the typical values for other children in the same age group and interpreted as such.
Another important thing to keep in mind is that BMI is simply an indicative unit of measure that reflects on your weight. It is in no way a diagnostic tool.
It is only a numeric value that indicates whether a person is fat or thin so that a doctor can discuss weight issues and find solutions for the same. It only shows whether you need to do something about your weight to reduce your risk of developing certain health problems.
A doctor correlates BMI with other assessments to determine the health risk of an individual. The recent guidelines suggest that BMI should be read in tandem with waist circumference and specific individual risk factors for disease.
Is BMI an Accurate Way of Measuring Body Fat in Athletes?
Body Mass Index or BMI is considered to be a standard for figuring out the ideal weight for your height.
The same BMI chart that is used for men applies to women as well, but there are limits to the same. For example, the accuracy of BMI is doubtful in the case of athletes and bodybuilders.
Muscle is denser than fat and weighs more. This can lead to wrong BMI counts on occasion. That means that an athlete may show a higher BMI, but may still have less body fat.
High BMI in the case of athletes is not necessarily an indication of obesity or below average health. In fact, if BMI was the only consideration, most Olympian athletes would be considered to be obese.
At the same time, it should not be taken for granted that a sportsperson cannot be overweight or obese. Even athletes can be overweight and at risk of developing obesity related medical conditions such as diabetes and heart disease.
Body Fat Measurement for Athletes
The problem with BMI is that it cannot differentiate between body fat and muscle mass, so how does one determine whether an athlete is overweight or not? A more accurate measurement is to look at body composition. Body composition is made up of body fat, bone mass, muscle and water. There are a number of methods other than BMI that we can use to measure fat content in athletes:
- Skin fold measurement using callipers
- Bioelectric impedance
- Water weighing
- Bioelectric impedance
- Dual-energy x-ray absorptiometry
- Computerised tomography
These alternate measurements are more accurate, and athletes with high BMI need to get their body fat composition checked using any one of the above measurements. It is also recommended that an assessment of health risk be conducted on the basis of diet evaluation, level of physical activity, family history, and any other medical tests that may be necessary.
What is the Most Popular Way of Measuring Fat in an Individual?
Definition and facts about Body Mass Index
The amount of body fat in an individual can be measured by a variety of different methods. Body Mass Index (BMI) is used to measure the amount of fat in an individual and is preferred over other methods because:
• BMI offers ease of measurement
• It requires only the measurement of the height and weight of the individual
• It does not require the help of an expert
• It is relatively inexpensive and does not require special equipment
Another advantage of using BMI to measure fat in an individual is that it allows health providers to calculate the risk of health problems such as heart trouble, diabetes, and stroke with minimal effort. However, this method does have its limits.
The main disadvantages are listed below:
• It is not very accurate and not preferred when more accurate readings are required
• It can overestimate the amount of body fat in athletes with a muscular build
• It can underestimate the body fat in older people who have lost muscle mass
In cases where a more accurate measurement of body fat is required, the following methods can be used:
• Computerized tomography
• Measuring skin fold thickness with calipers
• Underwater weighing
• DXA or Dual-energy X-ray Absorptiometry
• Bioelectrical impedance
The above methods also have certain disadvantages, such as:
• More expensive
• Require special equipment or expertise
• Not accessible to everyone
Reference charts for interpretation of BMI value
The BMI measurements are used along with other measurements such as waist circumference. There are different ways to compute BMI. This includes a simple formula of using standard BMI charts for either children or adults and using a BMI calculator. These reference charts are the same for both sexes and apply to individuals belonging to any age, race, or ethnicity.
Individuals are classified based on their BMI values as being underweight (below a value of 18.5), normal (between 18.5 and 24.9), overweight (25.0-29.9), and obese (30.0 and above). Individuals that have a BMI value of below 17.5 may be anorexic and recommended for further tests.
In children, the growth rate is measured according to their percentile ranking on standard charts, which is different for young boys and girls. This ranking denotes the position of the girl or boy compared to other boys and girls of the same age and sex.
Children with a normal weight and height fall between the 5th and 84th percentile. Children below this range (less then 5th percentile) are considered underweight, and those above 85th percentile and below 95th percentile are deemed to be at a higher risk of becoming overweight. Children who are equal to or greater than the 95th percentile are considered to be overweight.
Unless a more accurate measure of the person’s body fat is required for special diagnoses, the BMI is taken as the most convenient measure as it can be used for both genders and for people of different races and ages.
What are the requirements for measuring BMI?
In order to calculate the BMI (Body Mass Index) of an individual, there are only two basic requirements – the height and weight of the individual. Although the method of calculation is the same for people of all ages, it is interpreted in different ways. This calculation is very convenient and does not require any special equipment.
What is the purpose of calculating BMI?
BMI is calculated to get an idea of the fat content in the person’s body. Although this is not the most accurate way to measure fat, it is the most preferred method. BMI measurements are frequently used to interpret one’s health.
Based on the BMI numbers, health providers can advise patients about health risks they might face in the future.
Formula for BMI
There are different ways to measure body fat, with BMI being the most inexpensive of all. The formula for calculating BMI differs depending which system one is following, i.e. the English or the metric system.
English System for Calculating BMI
The formula for calculating BMI according to this system is:
Weight in pounds (lbs) divided by height measured in inches (in) squared, and then multiplied by a conversion factor of 703 [(Wt in lbs/ (ht in inches )2] 703.
It is very easy to compute the BMI by this formula. Measure your weight and height in the units mentioned in the formula. Now, divide your height by the square of the height and multiply the result by 703.
An example is as follows:
Height of the person: 65 inches
Weight of the person: 150 pounds
BMI [150 / (65)2] x 703 = 24.96
Calculation of BMI using the metric system
In this system of measurement, the weight of the individual is measured in kilograms (kg), and height in centimeters (and converted into meters before entering it into the formula).
The formula is the weight in kgs divided by the square of the height in meters. The value is then rounded off to the second decimal place.
An example is as follows:
Height of the individual: 165 cm (which is 1.65 m)
Weight of the individual 68 Kg
BMI calculation: 68/ (1.65)2 = 24.98
How can you determine health by calculating BMI?
The numbers computed by the calculation of BMI do not mean anything unless you compare it to the standard BMI chart. For adults above the age of 20, the standard weight categories are the same for all men and women and are as follows:
BMI below 18.5: Underweight
BMI between 18.5-24.9: Normal
BMI between 25.0-29.9: Overweight
BMI 30.0 and above: Obese
These standards differ for children below the ages of 20 and are plotted separately on the growth charts for both boys and girls, and a percentile ranking is obtained for them. This ranking indicates where the child stands in comparison to other children of the same age group. The growth chart for young boys and girls is shown below:
BMI less than 5th percentile: Underweight
BMI between the 5th and 84th percentile: Healthy
BMI between the 85th and 95th percentile: Risk of becoming overweight
BMI equal to or greater than the 95th percentile: Overweight
Although BMI calculations are used quite frequently, it should be kept in mind that there are other methods to accurately measure the amount of fat in an individual.
What do the computed values of BMI indicate?
BMI or Body Mass Index is a method by which health providers can determine if patients are underweight, healthy, or overweight. For instance, if the person has a BMI value that falls between 18.5-24.9, it is considered healthy. Those with a BMI above 24.9 are overweight, while those who have a BMI less than 24.9 are underweight. There is also a way in which the health of children can also be assessed with the help of BMI. In children, values that fall between the 5th and 85th percentile indicate a healthy child.
Advantages of measuring BMI over other methods
There are several methods to measure the level of fat in individual, but BMI remains the most convenient of them all. This is because only two measurements are required to calculate it, i.e. the height and weight of an individual. In addition, there is no special equipment required, and the results can be interpreted easily.
The main purpose of measuring BMI is to allow health providers to predict any health problems that the individual may suffer from in the future.
Limitations of BMI
Although BMI can be an indicator of health, there are several limitations in this method. For example, it can end up underestimating the body fat in older people who have less muscle mass and conversely overestimate body fat in athletes with a muscular build. Health providers usually keep these factors in mind while treating patients who are at “high-risk “and use other methods to assess their health.
Statistics regarding BMI
Research shows that less than half the adult population in the United States (about 68 million) has a healthy BMI. About 37 million women within the age group of 20-74 have healthy BMI. This number is less for men in the same age group – 31 million of whom have a healthy BMI.
Another set of statistics indicates that an alarming130 million in the USA are obese. This accounts for about two-thirds of the adult population who have a BMI of 25 or above. Anything above the value of 30 denotes obesity, and statistics reveal that about 6 million people in the US are obese.
This list includes adolescents and children, 15% of who are also overweight, and an additional 15% who are at high risk range of becoming overweight.
How can you determine that your BMI falls in the ‘healthy” category?
How are BMI and Obesity Linked?
Body Mass Index or BMI is an indication of the measure of fat in a person. Although it does not directly calculate the amount of fat present in the person, it is popularly used to measure the risk factor associated with several health problems such as diabetes, heart disease, and strokes that arise due to obesity.
Measuring your BMI is extremely easy and does not require the help of an expert. This method is preferred over other methods, unless very accurate measurements are required for health reasons.
Measurement of Fat
Although BMI is a preferred way to measure fat content, it can result in inaccurate measurements in certain individuals. For instance, in athletes who have a muscular build compared to other individuals, BMI can sometimes overestimate the amount of fat.
Similarly, in older people who have lost their muscle mass, the BMI may be higher. This method can therefore be inaccurate when it comes to accurate fat measurement.
Other methods that can be used to measure fat include skin fold measurements with the help of calipers, bioelectrical impedance, DXA (Dual energy X-ray Absorptiometry), computerized tomography, and underwater weighing.
These methods may yield more accurate measurements than those obtained by BMI, but are more inconvenient and require the presence of a trained professional and are therefore not accessible to many individuals.
Calculating BMI
You need two key measurements to calculate BMI – the height, as well as the weight of a person. There is a simple formula for calculating BMI which applies to both sexes, and people of all ages, ethnicity, and race. BMI can also be calculated with the help of a chart or calculator.
Determining the health of adults based on BMI
Since the calculation of BMI is based on only two sets of measurements, i.e. the height and weight of the individual, there are no separate charts for men and women, and the same standards apply for both sexes:
• A BMI value below 18.5 denotes that a person is underweight (if it falls below 17.5, it can denote that the person is anorexic)
• A BMI value between 18.5 and 24.9 is considered normal
• A BMI value that lies between 25.0-29.9 means that the person is overweight
• A BMI value of 30.0 and above indicates that the person is obese
BMI measurement for kids
Health providers use BMI measurements for kids and teenagers, plot these numbers on age-growth charts, and obtain a percentile ranking for each child. This is used to understand the child’s growth as compared to other kids in the same age group.
The results are compared against a standard growth chart for kids, after which the rate of growth in these kids and teenagers is determined.
Children who are below the 5th percentile are considered underweight, kids that fall between the 5th and 84th percentile are considered healthy, those that fall between the 85th to less than 95th percentile are at risk of becoming overweight over time, and kids who have a percentile above 95 are considered to be overweight.