Umm...well...
I hate to start by confessing I have not read the suggested book by Bright, but in my defense Ive been a student of fasting for decades, read many of the oldtime textbooks, worked at a fasting resort....
Adding to the above the decades of walking with Jesus:
It is mostly all about motive:
Are we fasting to force Gods hand, either His timing or provision, or have we been led of the S(s)pirit?
I used the word "mostly" because in the times of Christ and before, their fat cells did not contain the literal hundreds of toxins, heavy metals, etc. that in today's bodies will be released and have to be dealt with by our liver, kidneys, etc. All the more reason to be certain we are walking in and by the S(s)pirit.
Im also greatly concerned with how someone reconciles the Biblical warning to fast in secret vs. today's "tweet mentality."