Australasian Science: Australia's authority on science since 1938

The “Obesity Paradox” Paradox

By Tim Olds

Three recent studies have cast new darkness on the paradox that overweight adults are more likely to get diseases such as diabetes yet seem to live longer.

The full text of this article can be purchased from Informit.

I have written before about the Obesity Paradox – the finding that overweight adults are more likely to get diseases such as diabetes yet are less likely to die from them. In fact, overweight people appear to live longer. Now three recent studies have cast new darkness on the Obesity Paradox.

But before we deal with these studies, let’s review what we already know. The relationship between fatness (usually measured by Body Mass Index, or BMI, which is your weight in kilograms divided by your height in metres squared) and your risk of dying from anything at a given age is U-shaped. People who are very thin or very fat are more likely to shuffle off the mortal coil.

The issue is where the bottom of the U occurs. Traditionally it was thought to fall in the “normal weight” range (a BMI of 20–25). Recent analyses suggest it falls in the middle of the “overweight” range (BMI 25–30). This is a difference of about 10 kg for an average male, so we’re talking about quite a bit of lead in the saddlebags.

Now there have been three theories to explain the Obesity Paradox. The first is the Healthy Survivor Theory. To understand this theory you need to know how these epidemiological studies are done. Researchers get a group of people, measure their fatness and follow them until they die. Typically, researchers start following people in their 50s or 60s.

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The full text of this article can be purchased from Informit.