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When it comes to health, appearances can be deceiving. Despite our cultural obsession with thinness, being slim doesn’t automatically mean you’re healthy, nor does being in a larger body mean you’re unwell.
The widely used Body Mass Index (BMI) reinforces these health myths by offering a one-size-fits-all measurement of health risk. But research shows BMI is not only imprecise, it can also be discriminatory, particularly in a multicultural country like New Zealand.
Initially developed in the 1830s by a Belgian mathematician, BMI was never intended to assess individual health. It simply divides a person’s weight in kilograms by their height in square metres. From this calculation, people are categorised as “normal weight,” “overweight,” or “obese.” Strangely, while there is a consensus in medical research that BMI is a poor measure of body fatness, it is still used in New Zealand to determine access to publicly funded medical treatments.
The Ministry of Health’s most recent Clinical Guidelines for Weight Management for New Zealand Adults (last updated in 2017) acknowledge some of these limitations, noting that “BMI may not be as accurate an indicator of overweight in highly muscular people or in those with a smaller body stature.”
However, the guidelines still support the use of BMI as a population-level screening tool and do not recommend adjusted BMI thresholds for Māori or Pasifika communities. According to a Ministry of Health spokesperson, “at the time that the guidelines were updated, there was no evidence that higher cut-offs for Māori and Pacific were justified with regard to cardiometabolic risk factors.”
Yet this claim appears out of step with the scientific literature even at that time. Research dating back well before 2017 had already identified significant ethnic variations in body composition. For instance, a 2009 New Zealand study found that an Indian man with a BMI of 24 had the same body fat percentage as a NZ European with a BMI of 30 and a Pasifika man with a BMI of 34. Yet while the Indian man falls into the “normal” weight range, the others are classified as “obese.”
These types of misclassifications have real-world consequences because BMI remains a gatekeeper in New Zealand’s public health system, with eligibility for everything from IVF to post-cancer breast reconstructions often tied to BMI cut-offs.
According to “Sized Out: Fatness, Fertility Care, and Reproductive Justice in Aotearoa New Zealand”, a report by George Parker, a lecturer at Victoria University, the clinical priority access criteria for infertility treatment includes a BMI requirement that automatically excludes individuals with a BMI above 32 kg/m². This policy has been criticised for being outdated and unethical, as it does not account for variations in BMI among different ethnic groups and can lead to stigmatization and discrimination, particularly against Māori and Pacific women.
It means BMI cut-offs can give greater access to NZ Europeans and Asians, while disproportionately excluding Māori and Pasifika—deepening health inequities that no amount of clean eating or gym memberships can fix. Globally, similar disparities have been found. For example, while African American and white men in the United States have similar BMI-based “obesity” rates, body fat scans show white men have significantly higher levels of fat.
More concerningly, BMI is an especially poor predictor of health risk in non-white populations. Otago researchers found that while BMI correlates with harmful fat around the heart in New Zealand European men, it doesn’t for Māori or Pasifika men. This kind of fat—called epicardial adipose tissue—is a known marker for cardiovascular disease. Thus, BMI fails to identify this cardiovascular risk for Māori and Pasifika.
Even beyond ethnicity, body weight is a poor predictor of health. Studies show weight loss doesn’t reliably improve blood pressure, cholesterol or glucose levels. Instead, physical activity and cardiorespiratory fitness are linked to more significant reductions in mortality risk than weight loss.
In fact, people in the “overweight” category often live longer and survive chronic illness better than those at a “normal” weight. Simply put, weight isn’t a reliable measure of health and losing weight doesn’t guarantee better health.
While the Ministry of Health advises clinicians to consider a wider range of factors alongside BMI at the individual level, in practice, BMI remains the starting point and too often the gatekeeper for clinical decisions and access to our rationed public healthcare system. When used as a screening tool for access to treatment, its flaws disproportionately affect those whose bodies fall outside narrow norms. In doing so, it reinforces existing power structures by privileging New Zealand Europeans (and Asians), whose body types align more closely with BMI norms, while disadvantaging Māori and Pasifika communities.
BMI is not just a medical issue; it’s a political one. Decisions about publicly-funded healthcare are made based on a measurement that is demonstrably biased against certain ethnic groups. Anyone serious about equity in publicly funded healthcare must be willing to interrogate the racialised assumptions baked into the system. Because when BMI is used to ration care, it isn’t just a health metric—it becomes a mechanism for distributing privilege.
It’s time to move beyond BMI and our national fixation on thinness. Health is about more than body weight, a fact long acknowledged by holistic frameworks like the Māori model of wellbeing, Te Whare Tapa Whā, and the Pasifika model of health, Fonofale. These approaches recognise that health encompasses mental, social, and spiritual wellbeing, not just numbers on a chart.
So as we rethink how we define and measure health, let’s also challenge the myths we carry—about what a “healthy” body looks like, and who gets to be seen as healthy because real health doesn’t come with a dress size or a number on a chart. And it certainly doesn’t come in one colour.
As well as Jennifer Bowden’s columns in the NZ Listener, listener.co.nz subscribers can access her fortnightly Myth-buster column which explores food and nutrition myths.
