If one has "metabolic reserves", maybe something like the VCO fast is practicable, but for someone with metabolic problems, it's wise to stick to square meals of carbs, protein and fats.
Also, animal fats are a critical part of the diet - fatty meat, egg yolks, butter, bone marrow etc. This is where we got our fat-soluble vitamins as hunters...Read the Weston Price Foundation article "Guts and Grease" about the native Americans...(Google it!)