Sure, you can blame the ice cream, white bread, French fries, and processed meats all you want for our belly fat, but it turns out that there is another, more scientific culprit.

A new study out of City of Hope, in conjunction with researchers at UCLA, has identified what looks like a biological trigger for age-related belly fat — not just "you're older and your metabolism is slowing," but a specific cellular mechanism.

It is an important issue because belly fat is correlated with heart disease, diabetes, liver problems, some types of cancer, and risk for sudden death, in ways that other fatty deposits in the body are not.

Scientists have long assumed that belly fat expands with age mainly because existing fat cells get bigger. But the City of Hope research team suspected something else was also happening: that aging bodies aren't just puffing up old fat cells, they're manufacturing brand new ones.

The researchers found the source. Inside fat tissue lives a population of stem cells called adipocyte progenitor cells, which are basically fat cells in waiting. The researchers found that aging appears to activate a previously unknown subset of these cells, which then go into overdrive producing new fat cells, with a particular fondness for the belly. The researchers observed it first in mice, then confirmed the pattern in human tissue.

Translation: your waistline isn't just growing because old cells are stretching out. Your body is activating new fat cells as you age. Regrettably, this is a mechanism, not a treatment. But identifying the switch is the first step toward eventually flipping it, and that's a meaningfully different starting point than "just eat less and exercise more," which is an important but not complete picture.