Our experience with trying to put fat ferrets on a diet is that it is
usually a waste (waist?) of time.  Fat ferrets, if given proper exercise
and lots of it, tend to lose weight on their own.  Sometimes they just drop
weight of their own accord without any encouragement.  Low fat "diet" cat
foods are harmful to ferrets since they lack the fat content necessary for
good ferret health.  We've done a little food restriction--only putting a
small amount in the bowl and not refilling until it is gone, but it seems
unnessary.  The ferret didn't lose weight this way, and then dropped the
weight spontaneously after we gave up on the restriction.  Certainly,
treats should be curbed, but increased exercise is the best way to try to
enforce weight loss.  Goes for us humans, too.
 
Ferret Rescue of the Western States
[Posted in FML issue 2602]