Intuition and Perogative: BMI for women

Body Mass Index bmi for women, female version

This post will be challenging some rather old-fashioned ideas surrounding body mass index bmi for women.

Traditionally the BMI chart for women is linear, however, this model is not an ideal or a true representation of the changes in a healthy weight for women according to age.

As most of us are aware by now, body mass index (BMI) has been a traditional way of measuring how healthy your body weight is in relation to your height. To calculate Body Mass Index you divide your weight in kilograms by your height squared in metres.

No need to worry about all that math. Calulate your personal Body Mass Index HERE with the Doctor’s very own bmi calculator.

Why thank you Moose. The body mass index calculator also takes into account your age and gender.

Chart for Body Mass Index BMI for Women

The chart below shows more curved lines that indicate how a woman’s body mass index changes with age. Quite interesting, really. I bet you haven’t seen this chart anywhere else!

Notice the “median” (or average) weight bmi value, which is the 50^th percentile Red line.

Is my BMI average?

Look on the chart, the red line at the 50th percentile is the average.

…or look at the numbers on the bottom of this page.

Traditional Criteria for Body Mass Index for Women

Compare the chart above to the Centers for Disease Control and Prevention (CDC) definitions of overweight according to BMI as below:-

A BMI of less than 18.5 falls in the underweight range
Body Mass Index of 18.5 to 25 is within the normal range
If your BMI is between 25 and 30 then it falls within the overweight range according to the CDC criteria
A BMI of 30 or over falls within the obese range

According to the above definitions, a healthy bmi for women is between 18.5 and 25. However, a woman with a body mass index of over 25 is in the overweight or obese categories. In other words, this is above the ideal body weight range.

Thus, this is how the experts came up with the famous, and often quoted, statistic that over 50 percent of American Women are considered overweight based on having a BMI of over 25.

However, these classifications do not take into account the age of women.

If you are interested, you can find out your ideal weight and how you compare to others, using the Doc’s very own Ideal Weight Calculator.

Comparison of the Nhanes III survey and the CDC criteria for Body Mass Index BMI for Women

Notice in the Nhanes III body mass index chart above, there is a gradual increase in the body mass index bmi for women over time. Furthermore, the BMI gently increases until the age of 50 to 60.

Obviously, this curved line may well take into account hormonal weight gain, both after pregnancies and also in menopausal women.

However, after age 50 to 60 a gradual decrease in BMI occurs in older women.

Interestingly, each percentile line has a curved shape, even for the very slim women (or those classed as a normal weight or even underweight) at the 25^th and 10^th percentiles.

I’m hinting, without much subtlety, that a curved line is a better model than a flat line across all bmi charts for women. In fact, I will go as far as saying that some weight gain during adult life is natural.

BMI charts for children

The BMI chart shows how for girls, the BMI increases with age, even after age 20.

The children’s data came from the standard CDC growth charts.

There is a gap between the children’s and adult data, because the data sources are different.

The adult data (from the NHANES III survey) is more recent ( 1988-1994 ), whereas the body-mass-index-for-age charts from the CDC are based from a mix of data from old and recent sources.

BMI charts for Men

Our page contents also show a body mass index chart for men (below).

Comparing man and woman BMI charts, you will notice some differences.

For men under the 50^th percentile the BMI is higher than for women. This is thought to be because men have a greater skeletal muscle mass.

However, after age 30, for the 50^th percentiles or higher, overweight women have higher BMI values than men.

Why is that?

Probably because body fat percentage is also an important factor if a woman is going to be overweight.

Indeed, BMI for women fails to take into account the full body composition. A woman’s body accumulates more fat in the breasts and hips, which are places that men’s fat accumulation doesn’t occur. This is why waist-to-hip ratio is also important.

This female trait probably explains the higher BMI in overweight women.

I realize that the charts can be a little hard to read, so the table below shows the actual numbers:

Age:	20-29 yrs	30-39 yrs	40-49 yrs	50-59 yrs	60-69 yrs
The “National Average” Median Body Mass Index values for Women are:
Median BMI:	24.4	26.4	27.8	28.4	27.5

Surf onward to:

Return to the Body Mass Index calculator for women,
Or to the mens BMI calculator,
Or see the Men’s BMI chart, (similar to this page)

January 29,2015 update. If you are over age 50, you REALLY ought to see this page, proving that having a BMI of 25 to 30 is actually the healthiest and reduces risk of death. This range of BMI is not actually overweight.

Questions and Answers

How to use BMI?

BMI is used as a screening tool that is a weight to height ratio to identify weight problems for adults. These include identifying if a person is underweight overweight and obese.

However, body mass index is not a diagnostic tool.

BMI for women can be used to determine if your weight is a risk factor for various health problem, for example high blood pressure and cardiovascular disease.

In addition, a healthcare provider may perform further assessments if your bmi is outside of the ‘normal’ range.

These assessments may include:-

Evaluation of diet
If necessary, advice on a healthy weight loss plan
Assessment of physical activity, and again, a healthy exercise plan
Medical family history
Possibly other health screenings such as testing for type diabetes or high cholesterol levels
Waist circumference measurements or waist-to-height ratio to find out if you are carrying too much belly fat which can be a health risk

Why use BMI to measure overweight and obesity?

Firstly, calculating BMI is one of the best methods for population assessment to determine if you are underweight, overweight obese or morbidly obese.

On the positive side, the BMI calculation only requires weight and height, it is not costly and it is also very simple to use for both clinicians and the general public.

Secondly, the use of BMI allows individuals to compare their own weight status to that of the general population.

Are there any other ways to measure obesity?

Other methods used to measure obesity include:-

Skinfold thickness measurement calipers
Underwater weighing
Bioelectrical impedance
Dual-energy x-ray absorptiometry (DXA)
Isotope dilution

However these methods are not always readily available because they are expensive or need highly trained personnel.

How reliable is BMI as an indicator of body fatness?

The correlation between Body Mass Index (BMI) and body fatness is fairly strong.

However it does vary according to gender, race, and age.

For example, at the same BMI, women tend to have more body fat than men and this is completely normal.

Furthermore, as we have seen earlier, older people, on average, tend to have more body fat than younger adults even if the BMI is the same.

In addition, highly trained athletes (including a female athlete) will tend to have a higher BMI because of increased muscle mass rather than extra body fat.

What is a healthy BMI?

As we have seen, BMI does vary according to age, gender and race, but the general guideline for a healthy bmi is between 20 and 25

What does your BMI mean?

To have a BMI under 18.5 is considered very underweight and possibly malnourished. However, a BMI of 18.5 to 24.9 is within a healthy weight range for young and middle-aged adults. Furthermore, a BMI between 25.0 and 29.9 is classed as overweight. Finally, a BMI over 30 is considered obese.

Are there any exceptions to the rule?

The BMI measurement can not differentiate between body fat and muscle mass. Hence, there are some exceptions to the BMI guidelines, for example, if you have a large frame size or are very muscular.

What are the health consequences of overweight and obesity for adults?

Hypertension or high blood pressure
Dyslipidemia (Cholesterol problems)
Type 2 diabetes
Coronary Heart Disease
Stroke
Gallbladder Disease
Osteoarthritis
Sleep Apnea
Respiratory Problems
Some cancers including endometrial cancer, breast cancer, and colon cancer.

Is BMI interpreted the same way for children and teens as it is for adults?

Yes, but the criteria used to interpret BMI numbers for children and teens is different from those used for adults.

Finally, for children and teens, BMI age, and gender-specific percentiles are used for two basic reasons:

The amount of body fat changes with age
Also, the amount of body fat differs between boys and girls

According to the BMI chart I’m too short!

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