Heavy D -- Over 300 Pounds When He Died

Heavy D weighed 344 pounds at the time of his death yesterday ... law enforcement tells TMZ.

Officials recorded Heavy's height and weight as part of their investigation into his sudden and unexpected passing. We're told the rapper measured in at 6'4".

Heavy famously lost 135 pounds back in 2003 -- but insisted the decision to drop the weight was in an effort to get acting roles ... and wasn't health related.

An autopsy is scheduled to begin this morning.

TMZ broke the story ... Heavy D died yesterday after collapsing outside of his Beverly Hills condo.