No Longer Normal: The Absurdity of “Normal” Weight
“Normal” has a very succinct definition: usual, typical, or expected. So a recent publication in JAMA reminds us that the definition of “normal” weight is seriously broken. A weight in the range of a “normal” BMI (18.5 – 24.9) is no longer normal for young adults. The normal, typical, or average weight for an American 18 to 25 years of age in 2018 is a BMI of 27.7.
Thus, labeling the range of BMI from 18.5 to 24.9 as “normal” is now just plain silly. Normal is 27.7 – regardless of what bias you bring to this subject. A BMI of 22 is unusual.
The shift in young adults toward obesity is dramatic. In 1980, six percent fell in that range. In 2018, that number was more than five times higher – 33 percent.
Preoccupied with Weight
An excessive preoccupation with weight status is not helpful. It has serves to equate weight with health and leads people to falsely assume they can judge a person’s health simply by their body size.
David Sarwer, director of the Center for Obesity Research and Education at Temple University, tells Helio that BMI is not useless:
“While BMI is flawed, it is still an important measure. Twenty years ago, many physicians were not calculating the BMI of their patients.”
It provides an objective starting point for clinical assessment and dialogue. But, he adds, it doesn’t tell you everything about a person’s health:
“For example, the typical patient who undergoes bariatric surgery loses about one-third of their weight and experiences dramatic improvements in their health. However, most of those patients still have a BMI that classifies them as having obesity, even though they are much healthier than they were 1 year ago.”
Putting Health First
For healthcare providers, weight is not irrelevant to a person’s health, but it is not everything. It is simply a clue to be alert for signs that adipose tissue might be setting a patient up for chronic diseases from the systemic inflammation it promotes.
Thus, newer guidelines for obesity care put health first. For some patients, the risk of complications from obesity will start at a lower BMI than others. Different patients will have different priorities for their health. One size does not fit all.
Still No Clue After Four Decades
But perhaps the most troubling aspect of these new data for obesity in young adults is the recognition that obesity rates have quintupled and health experts don’t really know why. Yes, it’s complex and it stems from many factors working in concert. But Alejandra Ellison-Barnes, Sara Johnson, and Kimberly Gudzune conclude their report by telling us that we need to get curious and figure this out:
“There is an urgent need for research on risk factors contributing to obesity during this developmental stage [young adulthood] to inform the design of interventions as well as policies aimed at prevention.”
Best guesses and glib eat-less-move-more advice are inadequate for reducing the health impact of obesity.
Click here for the paper in JAMA and here for further reporting.
Diana in the Autumn Wind, painting by Paul Klee / WikiArt
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December 6, 2021
December 06, 2021 at 7:08 am, Al Lewis said:
Even before COVID, the rate of hospitalizations for heart attacks and diabetes was not climbing. Clearly there is not anything like a 1-to-1 correlation with weight or it would have been rising at roughly the same rate but maybe lagged a bit.
December 06, 2021 at 9:04 am, David Brown said:
One reason risk of complications from obesity will start at a lower BMI than others is because of excessive polyunsaturated fatty acids in fat stores. Excerpt: “The researchers believe that what is referred to as the obesity paradox, or a perceived higher body mass index (BMI) threshold for severe acute pancreatitis in some patients, may be explained by composition of a person’s visceral fat accumulated before the disease. The rapid breakdown of this fat and the action of the released unsaturated or essential fatty acids during acute illness worsen the disease course. Their findings may also hold true for other serious conditions with sudden and rapid progression in which the ‘obesity paradox’ is described. https://advancingthescience.mayo.edu/2021/02/12/body-fat-investigation-provides-insights-for-obesity-paradox/
December 06, 2021 at 11:41 am, Ted said:
Thanks David for this interesting speculation. It’s worth remembering, though, that “believing” something to be true is not the same thing as knowing it to be true. Confusing speculation with fact in obesity and metabolic diseases is part of the reason that progress on understanding these diseases has been so slow to come.
December 06, 2021 at 2:38 pm, Katherine Flegal said:
Some historical perspective needed here. Back before 1998, the definition of ‘overweight’ was a BMI of 27.8 for men and 27.3 for women. What was this based on? It was based on the weights of men and women in their 20s. These BMI cutoffs represented the sex-specific 85th percentile of the BMI distribution for persons aged 20–29 y in the second National Health and Nutrition Examination Survey. This was recommended in 1985 . So why did the number 25 start to be used? This is generally described as “arbitrary.” So in 1985, someone with a BMI of 25 would not have been considered ‘overweight’ anyway.
December 06, 2021 at 3:38 pm, John Dixon said:
BMI is a good measure of body fatness not health. The WHO charts and the data that accompanied the introduction of BMI in the late 70s were not consistent.
A healthy weight for an individual is complex as it involved sex, age, ethnicity, state of health, weight trajectory and the chosen metric of health. Mortality risk, reproductive function, physical function, and mental function, are all important metrics, but optimal weight for health may vary in an individual depending on the metric chosen and throughout the life cycle.
BMI is an important metric if it is understood and interpreted for any individual. There is no BMI that is universally optimal for all and normal well it’s normal now.
We should focus on an individuals health respect their health goals.
The thinner the healthier mantra is a myth!