An excellent teaching on fasting/dieting/self image by Lisa Bevere called “Fast Forward -The Untapped Catalyst to Spiritual Growth.” This is based on her personal testimony.
Here is the intro:
“The Bible says God shares insights and secrets with those who fear Him (Ps. 25:14). Since this book is all about changing your focus from what you look like to what you see, it is only fitting that I discuss the ways you can sharpen your spiritual sight. Prayer and fasting are important ways to do this.
You may or may not be in a position to fast food. In fact, if you are taking medications of any kind (or you have been struggling with any symptoms of an eating dis-order, which you can find listed at the end of this book), I strongly advise you not to make any changes to your eating habits without consulting a health-care professional. However, even if you are unable to fast food, everyone is in a position to fast something.”