One way in which fasting, if observed with the correct mindset, can elevate our productivity and discipline levels is:
“When we learn to say “No” to our impulses we improve and strengthen the control our mind has over our body. When we discipline ourselves, for a determined period, we are reinstating control over our nafs and our limbs. In doing that, we start breaking the mental barriers that held us off in the past.” The Productive Muslim, Where Faith Meets Productivity, Mohammed Faris.
Something else to think about is how when we are not fasting, the time cost of repeatedly snacking etc can add up to be quite substantial especially when in the middle of a task rather than on a scheduled break. Studies show that there is a cognitive cost associated with this as it takes an average of 22 minutes or so to regain a level of engagement with an activity after being interrupted.
If we do not observe voluntary fasts outside the month of Ramadhan, we will soon fall back into our usual routines and the benefits described above may well be lost for 11 months of the year.