With respect to energy, that’s apparently true. However, metabolism has non-energy needs which are supplied through food: vitamins, minerals, protein, and some

With respect to energy, that’s apparently true. However, metabolism has non-energy needs which are supplied through food: vitamins, minerals, protein, and some fats that cannot be synthesized iirc. Though these needs are greatly reduced when fasting, they do not go to zero. Google “angus barbieri” for the most famous, though not unique, example for medically documented long term fasting.