I'll add a little anecdotal but personal story to the mix.
I ran in college and was a XC/10k/5k guy. I am pretty thin and have never had issues putting on excess weight, even in lower mileage times (work, kids, etc.) My wife is also think and pretty fast, to boot. She ran in college, too, but she was a XC/1,500/5k runner.
I immediately started running marathons after college while she stopped racing and just ran. After a while, she started doing other forms of working out (elliptical, yoga, barre classes, etc.). She actually lost weight after she started doing other forms of working out. She got leaner and less muscular, especially in the legs.
So fast forward a few years and we are married. She decides that she wants to run Boston with me, so she needs to train for a BQ. So she starts running more and we both go and race a marathon. She runs an easy 3:34 and qualifies for Boston the following year. She steps up training and probably maxes out at like 70 mpw leading up to Boston. She runs under 3:30 at Boston but over the entire 18-month process gains about 10-15 pounds.
After Boston, she goes back to her normal workout routine and the weight comes off. She was very aware of it at the time and she never looked bad, but it was something we discussed because it was so odd.
With regard to food, we didn't really do anything differently. This was before kids, so we had a pretty set routine and it wasn't like she was sneaking burgers or something. Yeah, calorie intake probably went up with the harder workouts but nothing crazy.
I cannot see this happening to me, but maybe it is specific to women?