Is BMI still valid for health risk assessment today?

The medical field is proud of its progress and innovation, but has been using medical calculus for more than 150 years to assess healthy body weight.

Has the body mass index (BMI) exceeded its value in determining the health and associated risk factors of an individual or community?

Health officials and academics admit that it is not the perfect system for measuring a person’s health, but many say that it remains valuable after all this time.

“It’s a tool that can open the door to other risk factors, and do you get enough sleep to have that conversation with patients, what is your stress, what are your eating patterns, and how do you go deeper. Looking at height and weight,” said Rebecca Mason- , head of clinical nutrition at Spectrum Health in Grand Rapids.


The weight of a person’s BMI is calculated by dividing their height by the square meter in kilograms. For adults, a BMI below 18.5 is considered underweight, while an index of 25 or higher suggests that an individual is overweight. A BMI of 30 or higher is considered obese, according to the U.S. Centers for Disease Control and Prevention.

When BMI was first used in the mid-1800s, it allowed physicians to relate some health risks to their body weight before developing tools to better measure body fat. Obesity and high body fat are associated with diseases and conditions such as diabetes, hypertension, heart disease, liver disease, osteoarthritis, stroke, and certain cancers.

Obesity has also been linked to impaired immune function and reduced lung capacity, which may explain why health care providers have noticed worse results in COVID-19 in overweight and / or underweight supplemental health factors.

Related: “We didn’t include a healthy population in this;” How COVID clarified the weight problem in Michigan

Of the 900,000 adults hospitalized with COVID-19 between the start of the pandemic and 18 November 2020, about 30% were considered obese, according to the CDC. Federal officials say obesity could triple the risk of hospitalization as a result of COVID.

Anecdotally, Michigan physicians have also noticed overweight trends in hospitalized COVID patients.

Clinicians often collect height and weight information about their patients, and chart tools will usually calculate the BMI automatically. But Mason said it is up to the individual physician to be open-minded and gather more information about lifestyle when assessing the patient’s health and potential risk factors.

“It’s important to make sure that doctors or healthcare professionals are trying to examine the whole person, not just that little data point,” he said.

A BMI above or below what is considered a healthy range should not be a diagnosis in itself. But rather, it triggers a conversation to assess a person’s sleep patterns, eating habits, mobility, and stress level.

“BMI is a useful tool for most people,” said Jim Pivarnik, a professor of kinesiology at Michigan State University, who has spent decades studying body composition and the body’s response to exercise. “It’s not perfect, but is it useful? Yes.

“You’re more right than wrong when judging someone’s obesity with BMI. Is it better now to measure your fat percentage? Absolutely.”

Related: Michigan man loses 100 pounds, throws diabetes after “miserable” fight with COVID

Taken alone, BMI can be imperfect, especially on an individual basis.

Take athletes with muscle mass and other people, for example. Body fat percentage may be within a healthy range, but the BMI suggests that they have unhealthy weight for height because muscle mass, body fat percentage, and bone density are also not taken into account.

This concept led Pivarnik to study the BMI of college athletes and non-athletes in 2007 to determine how accurately he could measure the percentage of body fat in an individual. A study published in the journal American College of Sports Medicine evaluated the body fat and BMI of 400 people and determined that the BMI did not provide an accurate picture.

“(GMI) is useless for contacting athletes,” Pivarnik said. “We know that some people are GMCs who may be overweight or obese, but it is clear that they are not.”

In recent years, more research has been conducted on differences in the body composition of different races and ethnic groups, which blurs the value and shortcomings of the use of BMI in different populations.

For example, black men and women generally have lower body fat percentages and higher muscle mass compared to white and Hispanic Americans. With this understanding, black populations can be mislabeled as overweight.

Mason also said that Asian populations may face health risks that start with a lower BMI than other groups. One study found that Asian individuals have an average body fat percentage of 3% to 5% higher than white individuals with the same BMI.

“One of my favorite things about medicine is that it’s constantly evolving and growing, and we knew 100 years ago that things change and change sometimes,” Mason said. “One of the things we’re noticing is that there are some ethnic groups where the GMI gives you a different picture.”

After noticing the flaws in using BMI to measure an individual’s health, Pivarnik said the data is likely to be more useful for analyzing population health and trends. He noted the CDC’s annual behavioral risk monitoring system, which randomly surveys people by telephone in all 50 states.

In 2020, according to surveys, Michigan ranks 35th among U.S. states in terms of adult obesity. The Michigan obesity rate was 35.2% above the national average of 32.2%.

In Michigan, only four counties reported adult obesity rates in 2019 at or below the national average, according to CDC data released last year. These include Washtenaw (29.4%), Oakland (30.7%), Leelanau (31.8%) and Ottawa (31.9%).

This means that 79 counties were above this threshold, with a rate of 33% or higher at 33%. Among the thickest counties are Saginaw (41.7%), Clare (41.6%), Montcalm (40.8%), Hillsdale (40.8%), Isabella (40.7%), Gratiot (40.6%). ) and Baraga (40.5%).

Below is a map of 83 counties in Michigan based on estimates of adult obesity rates. Hover over a county to see its rate based on the latest CDC data.

Can’t see the map? Click here.

Michigan has surpassed the state average for at least 30 years in a row until 1990. During this time, the obesity rate in Michigan has steadily risen from 14.1% in 1990 to 22.4% in 2000 and 31.7% in 2010.

Below is a map of U.S. adult obesity rates by state, based on 2020 data from the CDC’s Behavioral Risk Factors Surveillance System. Hover over each state to see the adult obesity rate and state classification.

Can’t see the map? Click here.

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