TMZ Sports has obtained the Dallas McCarver 911 call -- made by a friend who found the 26-year-old bodybuilder passed out in his apartment ... after apparently choking on food. 

The friend tried like hell to help McCarver -- performing CPR and other lifesaving maneuvers -- but he wasn't able to bring him back. 

The friend says McCarver had been taking Insulin -- and suggested he may have collapsed because of a medical condition related to the medicine, which usually treats diabetes. 

McCarver had collapsed onstage at a bodybuilding event back in March. It seems the friend believes McCarver may have experienced a similar situation while eating, which led to the fatal choking episode. 

McCarver was transported to a nearby hospital and was pronounced dead early Tuesday morning.