Researchers at the St. Louis University Liver Center have been studying the connection between a high fat, high sugar diet and fatty liver disease.

Fatty liver disease occurs when fat builds up around the liver and can damage it permanently.

The researchers experimented with mice, feeding them the mouse equivalent of burgers and fries and soda. They also made sure the mice just sat around instead of running around on those spinning wheels. In other words, the mice lived like a lot of Americans do.

After sixteen weeks or so they looked at the mice livers and saw that they'd doubled in size and had a kind of sickly, yellowish hue.

It's not certain that the same thing happens in people, but it at least suggests that it doesn't take long for fatty foods to fatten up the liver. Eat more healthful food, though, and the liver will slim down.