My suspicion for anyone losing this much weight this fast is that a big chunk is water weight. With a big change in diet there’s a good chance that the body wil

My suspicion for anyone losing this much weight this fast is that a big chunk is water weight. With a big change in diet there’s a good chance that the body will quickly find a new equilibrium with the amount of fluid cells will retain, especially since both salt and glucose are necessary for osmotic pressure in cells. I also suspect sudden weight loss from diet change can partially be attributed to mass within the colon. If you have 5 lb of dense food packed in your digestive system, and suddenly eat nothing but high fiber low calorie foods. You’re going to easily shed a couple pounds in the next day or two. If we assume half of the weight loss was not directly calorie related, a 1400 calorie deficit could easily be 1 american meal a day. Not totally out of the realm of possibility.