at 8 days I had already lost 7lbs or so. I assume most was glycogen and water. I'm not sure where you got 0lbs at 8 days, maybe from ticco? I started on 1/16 at 212-213 lbs. I weighed myself today, and came in 16lbs down, at 196.
Also, it is a transition back into solid foods. I'll be having 3 of my 6 meals a day as solid, and 3 shakes. Still keeping the carbs somewhat low, but not nonexistent. The only grains I'll be eating will be quinoa and oatmeal. Maybe a bit of whole wheat pasta every 4-5 days or so, but nothing ridiculous.
I'm not sure what you're talking about with the metabolites either. Amylase, protease and lipase are general terms for enzymes that break down carbs, proteins and lipids respectively. I've been consuming protein and plenty of fat and I've been having a shake with 50ish g of carbs 3x a week so there shouldn't be any significant downregulation of the enzymatic systems.