Why is it so easy to overeat fatty foods? Part of the answer may lie in a single protein inside the brain’s appetite-control cells — and a new study suggests it works differently in males and females.
Researchers at Osaka Metropolitan University, led by Shigenobu Matsumura, focused on OPA1, a protein that keeps mitochondria (the cell’s power plants) healthy in MC4R neurons in the hypothalamus — brain cells central to controlling appetite. Comparing normal mice with mice lacking OPA1 in those neurons, they found the OPA1-deficient animals ate more, gained more weight and became obese when given free access to dietary fat. The work was published August 13, 2026 in The FASEB Journal.
A striking sex difference
Fat exposure boosted OPA1 in male mice but not females, and the harms of losing OPA1 were more pronounced in females. Even the anti-obesity drug setmelanotide behaved differently: it curbed appetite in control and OPA1-deficient males, but worked much more weakly in OPA1-deficient females.
Why it matters
Obesity drugs are typically developed and dosed without much attention to sex-specific biology. “The sex differences observed…may help inform obesity treatment development and personalized medicine,” the researchers said. This is early mouse research, but it adds to evidence that men and women may respond differently to appetite biology and to the drugs that target it.