IMHO fasting has nothing to do with spirituality and I've done dozens of fasts  up to and including 40 day fasts.

Its hard as hell and your body will try and get you to eat every minute of the days, but the weight loss and awareness of your true inner strength make it worthwhile. 

 Some do it for the spirit, some do it for the mind, some do it for the body. 

In scripture it is used for spiritual purposes. 

I do think you are missing a key function of fasting if you don’t include spirituality. 

To each their own.