A total fast is very difficult - intermittent fasting (two fasting days a week, < 700 calories on a fasting day) works well and is easier. Read these articles by Dr. Mirkin, a sports physiologist and cyclist who uses intermittent fasting:
There's a book about it (but read the review below before buying):
The FastDiet - Revised & Updated: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting
by Michael Mosley
http://www.drmirkin.com/nutrition/weight-loss-with-intermitt...
http://www.drmirkin.com/nutrition/why-we-use-intermittent-fa...
There's a book about it (but read the review below before buying): The FastDiet - Revised & Updated: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting by Michael Mosley
https://www.amazon.com/FastDiet-Revised-Updated-Healthy-Inte...
Before buying the book, read this review, which gives tips and suggests that the book is unnecessary:
https://www.amazon.com/gp/customer-reviews/R30YI8D3RGZOFK/re...