Beyond BMI: Why Body Mass Index is Not a Reliable Indicator of Health
Apr 18, 2023Have you ever walked into a doctor’s office to get an x-ray referral or a script for antibiotics, and been surprised when the doctor brings up your weight?
Or have you gone to a yearly checkup, only to be told that the best thing for your *health* is to lose a couple of kilos without being asked for the full picture?
If so, you’re not alone.
Unfortunately it’s common for practitioners to prescribe weight loss as a catch-all for your health. The painful reality is however, that it can often do more harm than good to both our mental and physical wellbeing.
So why does this happen and what can we do about it?
What’s the problem?
GPs are a key part of helping us when we’re sick, but unfortunately their knowledge of nutrition can often be quite limited and even at times be infiltrated by diet culture.
They’re also often on a tight time limit, so when it comes to complex problems - like what, when and how much to eat - doctors generally don’t have the time to dive into nutrition with their patients, and all too often, people are left with the stock standard “eat less, move more” advice... not very helpful.
Not only this, but weight bias can play a big role in how you’re treated by your GP.
Weight bias is when people are treated differently depending on how much they weigh, particularly people in larger bodies. This is not only unhelpful for people who are coming to their doctor for help with problems that have nothing to do with their weight, but is also linked to worsening health, both physically and emotionally (1).
For example, one of my past clients, Rachel, lived with an undiagnosed eating disorder for ten years because her practitioners' weight bias led them to recommend fad diets, weight loss shakes, and medications instead of addressing the underlying issue.
This is just one of many examples of how weight stigma can be a factor in disordered eating and how making assumptions about people based on their BMI can do more harm than good.
Is BMI a predictor of health?
Overall, BMI is a pretty poor way to measure health and it really doesn’t tell us much at all about a person.
It is often used as a quick way to gauge someone's health, but it fails to provide a complete picture. BMI is a formula that compares weight to height and was intended to measure population changes and guide public health policy.
It was never intended to be used to measure an individual person’s health and does not measure the other, far more important determinants of health.
So why doesn’t BMI work?
To start, it doesn’t differentiate between muscle or fat. Someone who is more physically active might have more muscle, which might mean a higher BMI, but this doesn’t mean they’re not healthy.
In fact, gaining muscle is overall a positive sign, and not an indicator of poor health. BMI also doesn’t tell us about blood pressure, hormones, stress levels, sleeping habits or our relationship with food and our bodies.
Unfortunately, because it’s quick and easy it can sometimes be one of the only things measured when visiting a doctor and can often leave us feeling flat, deflated and victimised.
The truth is, you can be healthy at a higher weight, and unhealthy at a *healthy* weight - in fact, despite what many people think of when they think of an eating disorder, approximately 85% of people with an eating disorder aren’t underweight (2).
In fact, intentional weight loss often does more harm than good, especially in people that have ended up in the overeat-restrict cycle before.
Trying to restrict what you eat or attempting to lose weight quickly can get us stuck in a cycle known as weight cycling (where our weight goes up and down rapidly) which can be really hard on our bodies and increase the risk of inflammation, metabolic conditions and cardiovascular disease.
Not to mention, changes in weight can be caused by so many things - depression, stress, or underlying medical conditions can all impact our health, so we need to be careful when commenting on people’s weight - we don’t know what others are going through based on how they look.
Instead, engaging in healthy habits like meditating or getting enough sleep have been shown to have much more of an effect on our health than BMI - in fact, building healthy habits decreases mortality regardless of how much someone weighs (3).
So, what can you do about it?
If you feel uncomfortable with the way your doctor is addressing your weight, it's essential to have an open and honest conversation with them. Let them know how you feel and any worries you have about their approach. You can also ask your GP not to weigh you and find other ways to measure your health.
If your GP is not receptive, consider seeking support from other health professionals who are aligned with the Health At Every Size™ (HAES™) approach. Finding a dietitian or psychologist to work with can help you build a support network and find ways to improve your health without focusing solely on your weight.
If you're unable to access other health professionals at the moment, don't worry! You can begin your journey towards a healthier, happier you by joining the waitlist for the next round of Feel Good With Food, which will reopen in mid-2023.
This blog was written in collaboration with Melissa Joannou, a Nutrition & Dietetic Student and part of the Maddi Parsons Nutrition team. You can follow Melissa through her Instagram page.
