Interesting.

While there have been many reasons for obesity considered, the fact that the virus has this effect could help by studying it's effect directly, and the way it works in conjunction with things like inactivity and overeating. The virus may be sending a signal to the brain for it's benefit, to increase the amount of fat in the bloodstream, so strengthening the craving for fatty foods. It could also help explain why people 'bounce'-lose weight, and put it back on.