I guess it depends what your health reasons are? I just did my first prolon box and it was fine but I didn’t take any tests beforehand to compare. I was doing an 18/6 intermittent fast in the run up so I didn’t really feel that hungry as I divided the food into 2 bigger meals and ate in my usual window; I continued doing a decent walk of 4 - 6 miles fasted and didn’t start feeling hungry till the last day. I don’t know if it’s done any good though but I do hope so!
I don’t think you need products to not eat. I also think simply water fasting will have greater benefits over the same time span as the FMD. However, if that plan helps you stick to your fasts, do it.