I can't believe y'all are defending the venerable GM on this point, reparsing his words and rearranging them so that any bad interpretation was on the reader's end.
No, a fat comment doesn't give someone an ED.
Now add the fat comment on top of contempt for their gender-- largely beyond their control and, for women, historically the basis for all kinds of discrimination? I think it makes a difference.
GM certainly isn't single-handedly responsible for EDs among riders. But he spoke bluntly and gave free-rein to his dissing of women and others who weren't of the "Go Big or Go Home" variety. It would be very, very easy to feel belittled by him for things and impressed with the idea that if you were worth anything, you'd move Heaven and Earth to correct them in yourself. He wasn't the only person who spoke this way.... and was given credit for it.
I believe GM spoke in these old-fashioned terms about fat riders until the mid-1990s or so when the hue-and-cry from readers of his column in Practical Horseman reined in his rhetoric.