Tom Arnold -- Arnold Schwarzenegger Made My Penis Bigger

Arnold Schwarzenegger is officially in the penis enhancement business ... at least according to Tom Arnold, who says his junk looks BIGGER now because of all the weight he lost using Schwarzenegger's supplements.

As we reported, Tom says he lost 90 pounds in a matter of months thanks to exercise and diet -- including Schwarzenegger's new line of supps -- but added the biggest benefit was in his pants ... because now his penis looks bigger.

You gotta hear Tom's description of his enhanced look ... it's hilarious. He also says he and the wife are planning to go for baby #2 soon. Great timing.