Then it can be argued that people who make such statements don't know what they're talking about. Sadly, fasting isn't as popular as it used to be for one thing. The other is, that people who ARE motivated to fast and willing to do it, are already likely taking other action as well.
Making the assumption that people who fast and pray don't do anything else is baseless. You have NOTHING on which to base that accusation.
[Not trying to be a rough pile-on because I do appreciate frankness.]
Saladin religiously fasted so much that it ultimately killed him. He was quite an achiever. Jesus also fasted. Talk about an achiever!