If you’re trying to find your place in line for the COVID-19 vaccine, you’ll want to calculate your BMI. Shorthand for body mass index, it’s used by the Centers for Disease Control and Prevention to define obesity, one of the underlying medical conditions that puts people at greater risk of complications from COVID-19. Under Washington’s vaccine rollout plan, anyone over the age of 16 who has at least two underlying medical conditions — a BMI greater than 30 would count — will be eligible during Phase 1B, Tier 3, expected to begin this spring or summer.
But what does BMI really tell us? On its own, not as much as you might think.
Developed by Belgian mathematician and sociologist Adolphe Quetelet in 1832, the index is a mathematical formula that was later revised and named the body mass index in 1972 by Ancel Keys. At nearly 200 years old, the index is still used widely by health systems and governments today because it’s an inexpensive and easy tool.
The formula takes a person’s weight in kilograms, divided by the square of height in meters. (Not a math whiz? There’s plenty of BMI calculators online, including on the CDC’s website.)
According to 2019 data self-reported to the CDC, 28 percent of Washingtonians were obese; if they have another medical condition as well, they will have access to the COVID-19 vaccine ahead of the general population. Some states have offered vaccines to people solely based on a high BMI.
A high BMI can be an indicator of a level of body fat that puts an individual at risk for diabetes, high blood pressure, stroke and an array of other conditions.
The key word: can.
‘Bigger body, but not obese’
A growing movement disputes that BMI correlates to health and advocates that people should love their bodies no matter what size.
On a recent Instagram post, pop star Lizzo stands in front of a mirror, rubbing her stomach and, well, talking to it.
“I love you so much. I love you so much,” she says in a video posted for her 9.8 million followers (username: lizzobeeating). “Thank you so much for keeping me happy, for keeping me alive.”
The caption to the video with nearly 3 million views told audiences that she had recently started talking to her belly, praising it, after previously wanting to “cut my stomach off I hated it so much.”
Lizzo, 32, has become an icon for people who follow the body positivity movement, which objects to the belief that healthy means thin.
“I think there’s a lot of positive messaging out there, like from Lizzo,” said Kaiser Permanente registered dietitian Kerry Martinson. “Everyone can’t have the same shape. It’s more about your life. Are you eating healthy? How’s your stress? How’s your activity? BMI doesn’t consider muscle or bone density.”
She pointed to one of the most famous examples of the BMI being flawed: Actor and former California governor Arnold Schwarzenegger’s BMI measured in the 30s during his body-building career. Many athletes have a high body mass index.
“You can have a bigger body, but not be obese,” said Karen Kennedy, a local certified nutritionist. “Obesity creates a metabolic health crisis and a whole host of other issues. But being a big person isn’t bad.”
A ‘blunt instrument’
Even though BMI is an imperfect measure, experts aren’t ready to toss out the index completely.
It’s a “blunt instrument” but still a helpful screening tool for population-level interpretation, said Melissa Martin, Clark County Public Health’s chronic disease prevention program manager. Data about obesity primarily comes from self-reporting on a national level. For Martin, the information helps identify geographic areas that need attention. Studies have already established that people of color and low-income families are more at risk for obesity than other groups.
“How we use (the BMI) is more to look at areas of the county where we might want to focus and find ways to engage in community-led solutions,” she said.
As for an assessment of individual health, many doctors and other health providers take BMI into account. A diagnosis of obesity is often why doctors refer patients to a dietician like Martinson.
“People see that term ‘obese’ and it can be really negative and make people feel bad about themselves,” Martinson said. “I try to be sensitive to that when I see someone. When it comes up, I don’t focus on it. When they ask, I try to remind them that you can be healthy and be in a bigger body, beyond what the medical chart says, to just look at the whole picture rather than one number.”
Kennedy has learned from some of her clients that BMI often prompts doctors to offer a boilerplate, too-simple solution: Get fit.
“The health problems can be dismissed as, ‘You just need to lose some weight,’ ” she said. “And not look at what possibly could be the underlying cause of that weight gain. … Instead of looking at weight as the cause of everything, you could look at it as a symptom of an underlying imbalance.”
Obesity, according to the CDC, puts people at risk of serious illnesses. But maybe, Martinson said, the BMI itself shouldn’t carry so much weight. As a dietitian, Martinson tends to look at how the weight is carried.
“If you carry your weight in the hips and legs and not the stomach, that’s the pear shape and that weight is less of a risk factor,” she said. “But if you carry your weight around the stomach — the apple shape — there’s more of a risk. Your actual health is improved by things like exercise and building muscle.”
And if a high BMI helps people get access to a COVID-19 vaccine, Martinson’s OK with that.
“It certainly would open it up to a huge amount of people,” she said. “That may be a win for someone who is defined as obese. I’ll vote for that.”