So, in other words, it's just peachy for people to starve themselves as long as it's for god? Why not show your love for god by doing good things like helping people or cleaning up the community? That's the way I would personally show my love- for humanity...
Some people express their love in a different way. It's all good, yours or theirs, just; well, apples and oranges. Each has its own aspects, and the difference may be seen as positive and negative. The people I described are both training 'good' characters (perseverance, resistance towards temptation) -for- God, and expressing
Of course, you were also right. To merely fast themselves without doing any good is NATO.
Think of it a bit like love between humans, only beyond that.
The above case (fasting without helping humanity) is like a sex-based relationship without intimacy or understanding or compassion. It's not a good relationship, even if some people would say 'it's a working relationship! We're doing fine!' RIGHT.
And even then the nature of 'love' itself varies, right? some people like to be supported, others like to be taught, another like to be restricted. Not the nature of love, but..the manifestation.
Some people like vanilla, others like all the kinkiness human has to offer. Of course, there's a line over there -SOMEWHERE-, but it's not exactly black and white too, no?
God(s/esses)'s love is One and Singular but facetious, thus humans take it in billions of shapes, as much as that One love has facets. And thus they give it according to what they know and have.