I am a short guy, but I've been blessed by the fact that I generally don't have to watch what I eat. So if you're asking about losing weight, I'm not sure I can really help.
But if you're just rusty and looking to "tune up", then I'd suggest a modest exercise routine, like you'd do at a basketball practice. Sit-ups, pull-ups, jogging and running.
And then work all the basketball games you can. That'll get you in shape, and improve your officiating at the same time
Honestly, I don't think working with weights will be of any help to you at all as an official. Unless you're working a prison league, which I know some guys do.
Chuck