Anyway, the second thing I said to myself was, "Wow, that guy looks a lot like Arnold." So I went and looked for the name, and instead saw Joe Weider , so I just assumed that the man in the photo was Joe Weider who just happened to look like Arnold.
Well, turns out I'm an idiot. Not only does it say Arnold Schwarzenegger on the middle-left there (albeit in small letters), it turns out Joe Weider was born in 1919, which woulda made him an incredibly good-looking 50 year old when these ads first started appearing.
Further research has this to say about Arnold and Joe Weider's relationship:
The first thing Arnold managed to do was work out an agreement with Joe Weider. Arnold would provide information on how he trained and allow Weider to publish photographs of him in his bodybuilding magazines. In exchange, Arnold got a small salary, an apartment and a car, but even better was that the arrangement provided Arnold the freedom to train four to five hours a day.
Source: Official Arnold Schwarzenegger website.
From Amazing Spider-Man #84, May 1970.
Interesting trivia for the day: Blogger knows how to spell Schwarzenegger, and knows when I spell it wrong.