[gen220]

These are totally fair points. I'd only quibble a bit that diet can be a big limiter for linear progress in running, depending on the kind of running you're doing.

At the time I was training, I was aiming for a marathon time that qualifies you for the Boston Marathon, as an example. (that's much more about muscle development than other forms of running). You can't consistently run a sub-7:00 mile for more than 3 miles without having a pretty regimented diet.

If you don't increase your protein intake dramatically, you'll get injuries while pushing for that pace, and if you can't push, you will plateau.

But you're right that you can go pretty far (maybe a month) without changing your diet in running training, depending on where you're starting from.