Yes, here's a link to an old book that talks about fasting and food combining:
Health via Food – Soil and Health Library

The lead-in to the food combining topic starts at page 113 of the PDF, in Chapter XVI where he describes the process of digestion. Note that the PDF page numbers do not correspond to those in the Table of Contents.

The most important thing is to avoid eating meat, fish or poultry along with grains or potatoes. The starchy foods require an alkaline environment for digestion, which begins in the mouth. However, animal flesh requires stomach acid. But when the alkaline starchy "mash" enters the stomach, the acid and alkaline mash will be somewhat neutralized and both types of foods will enter the intestines and either ferment or putrefy and release toxins.

A dear hypochondriac I know recommended the diet to me.