Fasting is new fashion. Good. Appreciated. However, only abstaining from food is not real fasting.
To understand real meaning of उपवास, we must first understand what is आहार ?
आह्नियते मनसा बुद्धयाइन्द्रिर्वा इति आहार: |
मन , बुद्धि अथवा इन्द्रियों द्वारा जो कुछ आहरण ( बाहर से भीतर ) संचय किया जाता है वही आहार है |
All our thoughts taking chaotic birth continuously in mind-womb, all perceptual inputs our senses encounter, all intellectual decisions we take and physical food, water and air we imbibe is आहार .
Only not eating or altering physical food habits, won’t serve the purpose for long.
What if I never change oil in my car?
Dirt will accumulate in the oil. The filter will remove the dirt for a while, but eventually the filter will clog and the dirty oil will automatically bypass the filter through a relief valve. Dirty oil is thick and abrasive, so it causes more wear.
Additives in the oil like detergents, dispersants, rust-fighters and friction reducers will wear out, so the oil won’t lubricate as well as it should.
If you take so much care for machine, why not same care for something that is beyond definition of machine? Your body. You senses. They need oil change events regularly.
Senses when used for obsessions, addictions and daily life stress, generates subtle and obvious stool (मल/મળ).
Fasting/Withdrawal from all sensory inputs, seclusion from the daily life, spending time with mother nature – they oil changing events.
Like a tortoise, retract regularly 
🙂
Do it regularly or pay the heavy toll. 🙂 (Y)
No oil-change event for body-senses => Inefficient senses => Failures in life. (Don’t argue that Americans are rich despite not doing fasting! 
😉 Failures and being wealthy are different things. Failure as in living meaningful life)
