Fat itself is a nutrient [1], providing one of the most important bodily requirements of energy. The body requires other nutrients as well, and has methods of storing them. Fasting does not mean going without them. The nutrients of most interest to fasting are probably essential amino acids which can not be synthesized and ionic electrolytes.
Free protein and amino acids only last a couple days in the body before being used for muscle or being irreversibly converted to fat. When necessary, the body can break down muscle to obtain essential amino acids.
The relevant electrolytes the body needs are sodium, potassium, and magnesium, which it maintains fairly deep stores of in the bones.
Free protein and amino acids only last a couple days in the body before being used for muscle or being irreversibly converted to fat. When necessary, the body can break down muscle to obtain essential amino acids.
The relevant electrolytes the body needs are sodium, potassium, and magnesium, which it maintains fairly deep stores of in the bones.
https://en.wikipedia.org/wiki/Nutrient#Macronutrients