Their mission was to solve a small but nagging mystery of Alzheimer's disease: How would the brain's ability to store information be affected if they "turned off" the obscure protein LRP1?
But Guojun Bu and his fellow researchers were in for a surprise. As they expected, mice whose brains had been wiped of the LRP1 gene showed Alzheimer's-like memory problems. But they also started to put on weight - fast.
The mice were lethargic. They were on their way to becoming diabetic. And they didn't seem to know when to stop eating.
In other words, they were a lot like the more than 72 million Americans who were obese.
Bu, a neuroscientists at the Mayo clinic in Jacksonville and the study's lead author, said the findings could lead to a treatment that attacks the genetic causes of obesity.
"People complain that for people who are obese, it's just a lack of self control," he said. "But this confirmed there's a strong genetic element that controls their appetite."
Or rather, reconfirmed. Scientists have long suspected that people's DNA has a profound impact on their waistlines, and a number of studies have proved them right.
Bu's research focused on leptin, a hormone that regulates fat storage.