I suspect elimination of treats would be thefirst order, as they are usually the culprit when dealing withoverweight bunnies. Next, after some time, one might considerreducing the amount of pellets by very small increments overa long period of time. Do not put bunnies on "crashdiets!" I've read that to do so is harmful to the bun'shealth.
One might feed a lower protein content pellet or even timothy pellets,as opposed to higher 18%+ alfalfa based pelleted feed. Ifyour bun doesn't get out of the cage often, place a 2" x $" board inthe cage, forcing it to jump overthe piece oflumberto access feed or water in order to encourage weightloss.
I would encourage you to do some research before you take any steps toinsure you are doing nothing sudden, nor detrimental to the buns healthand well being. Some breeds are naturally stockier thanothers, so make sure your bun is fat before your proceed.
Buck