Does Age Effect BMI?


BMI Basics

If you're at least 20 years old, your body mass index, or BMI, takes in your height and weight for consideration, but not your age.

For example, an older person will have more fat on their body than a younger person who has the same BMI. (Unless the older adult is spending a lot of time in the gym!) 

Age does affect an adult's BMI in many different ways.

See Related: Calculate Your BMI

From having different risk factors for such health issues as obesity and cardiovascular disease to other problems related to weight gain and other chronic diseases, the measurement of BMI, while it can predict health outcomes such as risk of death, cause of cardiovascular mortality, and other illnesses that affect large portions of the general population, does not always give the very best indications of whether a person is at a healthy weight or not. 

You'll learn just exactly how BMI measures the overall health risk of older adults, its benefits and drawbacks, as well as how specific mortality measurements and an older adult's BMI overlap.

By the end of this article, you'll know just how much older age affects a person's BMI, how older US adults are affected by health issues such as heart disease and at what rates as opposed to adults of a younger age, and how the appearance of issues of a metabolic nature can adversely affect an older adult's BMI, muscle mass, and many other indicators of their overall health profile. 

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BMI and health

The CDC states that an adult's BMI is a measurement of their weight, adjusted to their physical height. Medical professionals measure a person's BMI by dividing the person's weight (in kilograms) by the square of that person's height (in meters). 

The reason why many physicians and health professionals use BMI as an indicator of health is that it is an easy, cost-effective, and noninvasive method of measuring a person's body fat.

Unlike a lot of other procedures, measuring a person's BMI only requires their weight and height. Most adults can get accurate and reliable reports on their BMI on a fairly regular basis.  

How BMI is Used to Track Health Outcomes

Various medical studies have shown that these types of health measurements correlate highly with both body fat levels and the increased risk for certain conditions.

When a person has an elevated BMI, this can allude to future risks of both death and morbidity. It is for these reasons that measuring a person's BMI helps health professionals screen for obesity and many of its related conditions. 

Body mass index measurements are also useful and practical when it comes to matters related to public health. As public BMI figures became more available, it has allowed public health workers the ability to compare data across geographical regions, times, as well as different groupings among populations. 

Baseline characteristics by BMI category

The Ohsaki Cohort study was a groundbreaking research project published in 2006. The study looked at Japanese adults and the overall impact of health conditions such as obesity, as well as being underweight or overweight, and how those ailments and other illnesses can serve as strong predictors of an unhealthy BMI. 

The study concluded that Japanese adults who were obese needed and used the healthcare system at much higher rates than adults who were at a normal weight. The Ohsaki Cohort study also showed that at the baseline, about 10 percent of Japanese adults ages 65 years of age or older became long-term users of the Japanese healthcare system at higher rates than younger adults in the same study. 

All-cause mortality by BMI category

JAMA (Journal of the American Medical Association) published a recent study that found obese subjects to have significantly higher rates of all-cause mortality. That means that obese adults in all age groups had a much higher chance of dying from a wide variety of health conditions than adults who are of normal weight. 

There was some controversy over the findings of this report. The World Health Organization created its own categories for discussing public data surrounding BMI and its effects on public health.

Other national health organizations tweaked the World Health Organization's categorization of BMI, but even these tweaks haven't been heavily examined in quite a while. But the original results of the JAMA study largely stand on their own to this day. 

Considerations of age

How Age Influences BMI Measurement

While BMI acts as a pretty good health assessment when it comes to the measurement of a person's body weight, it is a far-from-perfect tool for a whole host of reasons.

Chief among these reasons is that BMI measurements do not take age into account. Nor do they take into account a person's gender. For these and other reasons, a person's body mass index is not always the best way to determine whether a person is at a healthy body weight or not. 

Ideal BMI Changes with Age

Older adults tend to carry more fat on their bodies than younger people. For this very reason, the weight change that happens as adults grow older is completely normal.

There is no one ideal weight for any adult of a certain height. Whether a person should embark on a weight loss or even weight gain program will depend on factors such as waist circumference, the body shape of the patient, sex, fat mass, and height. A medical professional such as a physician will take all these factors into account, along with their patient's age. 

BMI Differences: Men & Women

How they differ

How public BMI data differs between men and women in the United States depends on a few things. Among them is the prevalence of certain health conditions in the subjects. What studies have shown is that when the men and women who are examined are healthy, there is little difference in BMI data. 

The International Journal of Obesity found that among its female subjects, the prevalence of overweight women participating in the study decreased sharply when the health levels of the female subjects increased. With male subjects in the same study, BMI levels didn't really vary much. 

Why they differ

Public BMI figures differ markedly between men and women for a few reasons. Some of these reasons include the fact that men and women carry different levels of fat on their bodies, even when these subjects have healthy BMI measurements. Other reasons include the average height differences between men and women, body shape, as well as muscularity, and bodily proportions. 

How they change with age

Because of the fact that older adults 65 years of age or older stored higher amounts of fat on their bodies than younger adults and adults in other age groups, older adults could be at the higher end of the BMI spectrum for their height and still be considered healthy.

Senior adults at the lower end of the body mass index spectrum were actually considered to be at a slightly higher risk for conditions such as cardiovascular disease. 

The AM J Clin Nutr found that their study's association between all cause mortality and BMI tended to present itself as a U-shaped curve. As a matter of fact, the study's researchers also found that older subjects who experienced the lowest risk levels were those that had a BMI between 27 and 29. 


For all adults, keeping and maintaining a healthy BMI is of the utmost importance. But exact figures that correspond to BMIs for healthy adults will vary depending on a lot of factors, including age. Public BMI data doesn't differ much between healthy men and women.

While obese older adults have been found to use healthcare services at higher rates, other studies have also discovered that senior adults can have slightly higher BMIs than their younger counterparts and still find themselves with a lower risk for a whole host of health conditions. 

The BMI ranges that senior adults should aim for isn't exactly cut and dried. A healthy body mass index for an older adult will depend on conditions ranging from bodily proportions to height to muscle mass and body shape. Other aspects can also influence this range. For a better idea on good BMI ranges for your particular situation, see your physician. 

Synthesize the information above into a conclusion paragraph that links all of the factors discussed into a comprehensive statement regarding how and why BMI statistics do and should change with age.