Heidi,
 
I had good results running my fat ferret on a sort of indoor track.  I hung
a colorful toy on a leash and swung it in a slow circle about 7 feet in
diameter.  Ferris ran after it.  We did these training sessions about five
minutes at a time once or twice a day for a few weeks.  He slimmed down
quickly and hasn't chubbed out again since.
 
Good luck!
 
Vesna
[Posted in FML issue 2788]