but I think it's only really beneficial if you have enough body fat to convert to energy (as that's the fuel your body uses instead of calories).

Agree on that, otherwise it will start cannibalizing own protein, which is quite damaging.

General advice: check with your doctor if you have any medical conditions, and take the proper precautions if you choose this route.

100% agree.

Congrats on the 7 days water fasting, it's a huge!