The differences are in part of the hypothalamus, which is a brain
region that's involved in appetite and hunger.
In rats that are genetically prone to obesity, certain brain cells in the
hypothalamus don't grow as much and are less sensitive to the fullness hormone
leptin, compared with other rats.
Those patterns may gear those rats toward obesity, note the researchers, who
included Sebastien Bouret, PhD, of the University of Southern California.
"It seems [in the case of these rats] that appetite and obesity are
built into the brain," Bouret says in a news release.
That may mean that those rats would have to work harder not to become obese,
because their brains might not get the "I'm full, stop eating" signal
from their bodies.
But that doesn't mean that obesity is a done deal for those rats. Bouret's
team didn't put the rats on running wheels or make them diet to see if that would counter
their obesity inclination. And the findings don't mean that obesity is just
about the brain or genes. Behavior counts, too.
"It is increasingly accepted that obesity results from a combination of
genetic and environmental factors," Bouret and colleagues write in
February's edition of Cell Metabolism.