Medical professionals have long used body mass index (BMI) as a tool to determine an individual's general health. Using a simple equation based on the relation of a person's weight and height to calculate lean body mass, BMI classifies people as underweight, at a healthy weight, overweight or obese.
However, research suggests that this single measurement may not be the best indicator of health. So how do we measure what's healthy? That's just one of the questions that experts in healthcare, academia, media and other fields tried to address at an event held in the United States and hosted by The Atlantic and Abbott. As it turns out, there may not be an easy answer.
Tracy Middleton, health director at Women's Health magazine, offered one explanation.
"I think people have latched onto BMI because they can go online and figure out the calculation themselves," she said.
Some health professionals think this technique is outdated, while others appreciate its simplicity.
"BMI is an easy and cost-effective way to figure out someone's degree of health," said Dr. Rachel Bond, associate director of the Women's Heart Health Programme at Lenox Hill Hospital.
Dr. Carla Prado, a professor and registered dietician, agreed.
"We can't ignore how much we've learned from BMI," she said. "It works well for measuring levels of obesity."
As a research tool, BMI helps classify people of varying ages, genders, demographics and locations into basic groups based on fat or lean body mass — but beyond that, grouping people based on this single number may have its limits.
Potential Pitfalls of BMI
While many of the healthcare providers in the room identified the benefits of BMI, they also understood its limitations.
"Some of the problems with BMI are that health varies so greatly from person to person with the same BMI and the score doesn't take into account people with different body composition or fat-to-muscle ratio, like cancer survivors or bodybuilders," Dr. Prado said.
"As athletes, we always have a higher BMI because our muscle weight tips the scales," explained Sharon Monplaisir, a three-time Olympic fencer for the United States.
These nuances extend to South Asians as well. The World Health Organization has found that health risks typically associated with high BMI affect this demographic differently. South Asians with lower BMIs are more at risk for diabetes and heart disease when using traditional BMI calculations. As a result, BMI calculators modified specifically for South Asians have started to pop up. These findings highlight the pitfalls of the age-old system while underlining the importance of finding alternative ways to assess overall health.
The conversation turned to the important ways in which muscle factors into overall health, such as mobility and balance, strength, immunity and wound healing.
"We tend to focus on these arbitrary numbers, instead of behaviours," said Mary Jane Detroyer, a registered dietitian and personal trainer. "For example, if you don't have muscle mass, you can't get out of a chair."
Suzette Pereira, Ph.D., a researcher at Abbott, added, "Once you turn 40, you can lose up to eight percent of your muscle (mass) each year. Maintaining muscle is really important for movement and for metabolism."
The experts agreed that one's muscle mass could be a good indicator of their overall health because of how it directly correlates with quality of life. But how can a physician measure muscle health in a simple way?
There are several ways to measure a person's muscle mass, including MRIs, DEXA scans and portable ultrasounds. Yet something as simple as looking at someone's walking speed may be able to give physicians more insight.
"Gait speed, or how fast you can walk for a fixed time, is a strong indicator of people's health," Pereira said.
Research suggests that gait speed can help predict negative health outcomes and has even been associated with life expectancy in older adults. Performing a test to measure walking speed over a short distance could be an effective way to establish health status. Another indicator of muscle health is gauging a person's ability to rise from a chair without using their hands for assistance.
Heather Milton, a senior exercise physiologist at the Sports Performance Center at New York University Langone Health, suggested asking patients if they move regularly or are physically active to get an idea of how they're feeling.
"Those are simple questions that can be asked by a physician, regardless of BMI," she said.
The Bottom Line
The group stressed the need for a comprehensive perspective on health.
"When working with patients, I look at them as a whole, including family history, genetics and other variables," Dr. Bond said.
Dr. Donna-Marie Manasseh, director and chief of breast surgery at Maimonides Breast Cancer Center, agreed.
"In the end," she said, "assessing health status requires a scorecard that includes a range of things that are easy to measure."
While there is no perfect measurement to define one's overall health, multiple tools can work together to provide doctors and individuals with the most comprehensive information on the matter.
"We must continue to challenge the status quo and look at health from every possible angle, including addressing the importance of muscle health," Pereira said.
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