"After my teacher (Yang Chengfu) arrived in southern China, he was afflicted with diarrhea and vomiting due to the sanitation of the water and environment. He was hooked up to an I.V. for not very long before he passed away". The capabilities and technology of western medicine was very poor in the 1930's throughout China, therefore the treatment of illness (however so minor) was a tremendous problem in many areas in China" (from article posted by Louis Swaim)
There is the answer to the question. YCF got sick, medical conditions were not the best so he passed away. I think its a little unfair and disrespectful the fact that many people throughout the years have implied that master yang's level of acomplishment in tajiquan was not soo big, simply becuse he had some overweight issues in late years.
His contribution to the art, his teachings, and the fact tht so many of his student reached a very high level as martial artists proves his commintment to the art his knowledge and understanding, therefore his high level as a martial aritst.
There is one famous xingyi master from that same period, and I keep forgeting the name but I'll find it and post it later. Anyway, he was also a little "heavier" in later years, and even in his fifties he was still considered the deadliest fighter in the streets of Taiwan.
My first kung fu techer was huuugeee! and he could still perfom flawlesly dragon style kung fu and his fighting ability was extraordinary.
As martial artists and as individuals we need to seek the best and healthiest physical shape we can, but sometimes perople that due to genetics dont look so trim, can be as agile or even more agile that "model looking" guys. Specially if the have been trined in a true martial tradition and have reached the level of undersandong that master yang cheng fu had.
Back in my karate days, (long ago!) my sensei used to say "a fat guy is that person who is unable to move his own mass, no matter how small", otherwise, no matter how big hes in good shape.
Now, this sound a little weird, but the point is, martial ability sometimes is not directly related to weight!
By the same token, master cheng man ching or sun lu tang, who looked extremely skinny and fragile shoul be acused of not being good martial artists becuse of their weight! well...we all know how far from reality that affirmation is, as CMC and SLT are considered among the greates contemporary masters.