Bone Thugs-n-Harmony's Bizzy Bone -- Stop Calling Me 'Fat Ass'

Rapper Bizzy Bone from Bone Thugs-n-Harmony tells TMZ he lost 30 POUNDS over the past 4 months after embarking on a mission to stop being such a "fat ass." Mission accomplished.

So why the dramatic weight loss?

The rapper tells us he was determined to reinvent himself following a 4-year stint on probation -- stemming from unpaid child support -- and part of that process started with cutting the fat.

BB says the diet was simple -- he stopped eating junk food and cut down on the boozing. The result ... bye bye beer gut.

In the end, Bizzy went from 194 lbs to 165 ... and hopes to keep the weight off for good.

Thuggish.