Obesity may come in 11 different types, each with their own cause
Obesity could exist in many forms, which may benefit from different treatments and prevention strategies
By Chris Simms
18 July 2025
We may be starting to understand why some weight-loss strategies, like exercising, don’t work for everyone with obesity
Science Photo Library/Alamy
It turns out that obesity may be much more complicated than we thought, with the condition potentially existing in up to 11 forms, each caused by distinct biological pathways.
“It’s not just about the body mass index or the body appearance; it’s more about the biology behind it and how that is related to risk factors,” says Akl Fahed at the Broad Institute in Cambridge, Massachusetts.
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The World Health Organization defines obesity as having excess fat that poses a risk to health. Whether someone has it is worked out by calculating their body mass index (BMI), a measure of weight relative to height.
As not everyone with obesity has health complications, some researchers have recently suggested introducing a category of “preclinical” obesity. This splits people with the condition into two groups: those with symptoms caused by excess fat, such as breathing difficulties and heart problems, and those who don’t have symptoms, but may at a later date. However, these two categories might not be going nearly far enough, according to work by Fahed and his colleagues.
The researchers did a genome-wide association study on more than 2 million people with obesity, with ancestries from all over the world, in which they looked for links between genes and BMI, as well as waist circumference, waist-to-hip ratio and hip circumference. From this, they identified 743 genetic regions linked to obesity, 86 of which hadn’t been reported before.
