I’ve written a fair bit about food and health over the years. I have tried, occasionally with success, to counter some of the common misunderstandin

The Obesity Blame Game

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2025-01-12 12:30:07

I’ve written a fair bit about food and health over the years. I have tried, occasionally with success, to counter some of the common misunderstandings and bad science in the world of food. But there is one thing that I dearly wish I could get through to people, because it is the source of so much of that misinformation. It concerns obesity and why Blondie releasing ‘Parallel Lines’ didn’t cause a global health crisis. And frustratingly, it takes a bit of explaining.

It all comes down to a strange quirk of how we talk about obesity and body weight. We generally use a system of BMI measurements to get an impression of how much excess weight people in the population have. BMI is a flawed system, especially when used as a diagnostic tool for individuals, but as a measure of how body shapes are changing in a human population, it’s not that bad. We take someone’s weight in kilograms and divide it by the square of their height in metres to give us a number, which we can then use to compare against other people. In short, it is a rough measure of how fat people are.

The quirk comes not from that measurement, but from how it is interpreted at a population level. When anyone talks about changes in population body weight over time, they will not talk about changes to the average weight, or the average BMI. Instead, they will almost always refer to the percentage of a population who are overweight or obese. This is the percentage of people who have a BMI over 25 for overweight, or 30 for obese.