There are people in ketoland who have magical thinking about the diet. They believe that all of the extra fat they eat will get turned 100% into ketones and peed out as excess from their bodies. Should be really easy to falsify this view by eating excess fat and measuring ketone concentrations…
Truth is the body stores the fat you eat. If you burn it off that day then so be it. If you burn off more than that you lose weight. If you burn off less then that you gain weight. No magic even in ketoland. The calories created from ketone production are minuscule – maybe 10-20% of your daily intake. Enough to replace the glucose missing in the diet. Very little goes out as waste (breath and urine). The bit that goes out is due to the inefficiencies of the process which drop with time (hence the lack of color on pee sticks for many people).
Dr Ted Naiman is becoming well know for his well-crafted diagrams. His latest update to the Metabolic Fuels Diagram adds the pancreas to the picture.
The red circle seems to be general circulation via blood.