Genes play a central role in obesity. But if genetics and obesity are
closely related, why does it seem like more people are affected by
obesity now? There were very few people with obesity a hundred years
ago—so is obesity really genetic?
Our genes haven't changed much over the last hundred years. In fact,
they haven't really changed over the past 50,000 years. What has
changed is our environment.
As the geneticist Francis Collins puts it, “Genetics loads the gun
and environment pulls the trigger.” That means that genetic factors
and environmental factors may not work on their own but interact with
each other to produce a result.
We now live in a different environment compared to people who lived
a hundred or so years ago. We live with different types of stress,
food and technology. The modern world interacts with our genes, and
obesity is one of the results of that.
Professor Joseph Proietto, a researcher and clinician specializing
in obesity, explains genetics and obesity by asking us to think about
two pots. They are different sizes: one pot holds 5 litres while the
other pot holds 50 litres. The pots stand in the rain overnight and in
the morning, both pots are full of water.
When you look at both pots, you can see that the larger pot holds
more water than the smaller pot. Professor Proietto explains that this
is because the bigger pot was made to hold more water. “In other
words, you need both your genetic make-up (how the pot was made) and
the environment (the rain) to develop obesity,” he says.
