The following claim has been all over news, at least Russian ones, e.g. here (pardon the errors - this sounds like an English translation of the Russian text that was in turn translated to English, belying URL's domain name :))
In the course of the research, it was found that men with a Shoe size from 43 and above, not so often loyal to its mate, as men with smaller feet.
Studies conducted by psychologists Illicit Encounters suggests that the probability of cheating in the pair is higher the larger the leg of a young man. At the same time, men 40 Shoe size continues to be the most faithful companions of life.
This relationship was set by observations of the men who go to Dating sites.
Are men with shoe size 40 more faithful, and shoe size 43+ less faithful?
The article sounds like the source is some weak analysis by a dating site "expert", so I'd prefer answers rooted in something a bit more rigorous if available.