In layman's terms, Ralphie had high blood pressure and an unhealthy heart. Someone who is morbidly obese has a propensity for high blood pressure and Clark County Coroner John Fudenberg tells TMZ his weight was a contributing factor in his death.

We're told drugs and alcohol did not contribute to his death.

The Coroner has classified the death as natural.

TMZ broke the story ... Ralphie died in early October from cardiac arrest and after 6 weeks of battling pneumonia. He had performed at Harrah's in Las Vegas ... and the last time anyone saw him was before he walked into his room to eat Jack in the Box.

As we reported ... Ralphie talked about his pneumonia battle and appeared to be in no condition to meet and greet fans after his show, but did anyway.

Ralphie was 45.