Why reducing our wellness to a BMI number is hurting our health

BMI is based only on a person's weight and height.
Bill Kohut

BMI is based only on a person's weight and height.

OPINION: "You're overweight, borderline obese."

This was what Christopher was told when he attended his corporate health check. The person conducting the check went on to suggest that he take a look at his diet and perhaps think about healthy options. While they didn't come out and say "you need to lose weight", that was the clear implication.

And how did they arrive at this advice?

A 10-minute check-up in which Christopher was weighed, measured and asked to do some basic stretches to assess flexibility, along with completing a two-page survey about lifestyle habits and exercise. The data was fed into a laptop and his body mass index (BMI) was calculated.

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While the laptop and BMI formula gave the impression that this was a scientific test, the advice was anything but. Science, after all, isn't gospel. It requires critical thinking, analysis and interpretation.

Unfortunately, many of the people running these checks seem to have an unwavering faith in the tools of their trade. Despite asking questions about his lifestyle, the diagnosis and advice seemed to be reduced to a BMI number.

What the BMI calculation couldn't possibly account for – since BMI is a crude measure based only on a person's weight and height – is that Christopher has the physique of sprinter; all muscle and not a skerrick of fat to be seen.

The BMI app, and the person who relayed the results, also did not consider that Christopher goes to the gym six times a week, already has a highly restrictive diet, and is a recovering anorexic.

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Fortunately, this experience didn't trigger a recurrence of his eating disorder. But that's not the point. Given the lengthy and complicated path to eating disorder recovery, it could have.

Psychologist and director of BodyMatters Australasia Sarah McMahon says that providing negative feedback about weight can be extremely dangerous, particularly for people with a history of eating and body image concerns.

"We know that dieting is the biggest risk factor for the development of eating disorders so anything that incites dramatic weight loss could be very dangerous. And given weight is an emotive topic for most people, there is no such thing as 'tactful' feedback – regardless of a person's apparent psychological health," McMahon says.

Not only can this type of advice be psychologically harmful, it also unlikely to inspire people to adopt healthier lifestyles.

"There is an abundance of research to suggest that shaming people about their weight does not inspire behavioural change. Ironically, shame is likely to result in an avoidant coping style rather than promoting health-giving behaviour," McMahon says.

The person conducting Christopher's health check could have taken one look at him and realised that the suggestion to lose weight was ridiculous. Where was he going to lose it from? His big toe?

But even if he did have visible body fat, a health professional should not be giving advice based on one-dimensional and flawed evidence.

"BMI criteria is a terrible way to judge a person's health," says Rick Kausman author of If Not Dieting, Then What? and fellow of the Australian Society for Psychological Medicine.

"BMI started as a mathematical formula which was supposed to measure populations. It's morphed from something that was meant to be a best-guess indicator for population changes to something you use to assess individuals and their health. There is no evidence to support that whatsoever," says Dr Kausman, who has run a weight-management clinic for over 25 years and is one the board of the Butterfly Foundation.

Dr Kausman says that medical professionals can't judge if a person is at their most healthy weight just by looking at them.

"Do you diagnose anything else just by looking at a person? A rash maybe, but if in doubt but you'd do a biopsy."

Instead, health and nutrition professionals should be looking at more accurate indicators of health and focusing on patient attitudes and behaviours.

"Blood sugar levels and blood pressure are all much better measures than this all-encompassing BMI number which turns out to be based on falsehood. And questions like, 'Are you moving your body in an enjoyable way on a regular basis?' and, 'Are you eating a variety of healthy and yummy food most of the time?' are much more useful," he said.

Similar questions to these were asked in Christopher's health check, but yet, they weren't factored into the BMI result or the health advice he was given. The take-home message for Christopher was: "They said I was borderline obese."

Sarah McMahon says that even more harmful than using archaic measures such as BMI as "health checks" is how that feedback is delivered.

"If someone is told they are over (or under) weight, we need to be asking ourselves: over whose weight?" McMahon says. "The fact is that we all come in different shapes and sizes based on our unique genetic and ethnic history, and other factors such as epigenetics and our body composition."

Corporate health checks are seen as unquestionably good. They are even recommended by governments. No doubt employers think they are doing the right thing by providing corporate health check services for their staff. When employees spend a third of their life at work, then health should be a matter for corporate concern.

But if the process involves widely discredited diagnostic tools, and provides advice that can be demotivating and even psychologically damaging, then perhaps they are actually doing more harm than good.

Kasey Edwards is the best-selling author of Thirty-Something and Over It. kaseyedwards.com

 - SMH

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