A friend of mine who used to hike in the Pyrenees had incredible stories regarding hunger and eating.
They relied on a paper map only, no smartphones with GPS back then and they did not have any Magellan GPS. Taking a wrong turn somewhere, they added like 40 km to their intended trek, which in that terrain meant two days.
They ran out of food and she was so starved that she ate entire tube of her skin cream. Together with a few bugs that made their way into their tent.
Her description: it looked like yogurt with raisins, but I am not going to describe the taste.
No health consequences.
As for fasting. I fast sometimes, but I would not try fasting on a long hike in mountains like Pyrenees. Probably not even Tatras.