Lean body mass loss during caloric restriction may be due to reduction of water, gut tissue, liver tissue, and glycogen stores, not solely muscle.

“and a lot of i think what we see with lean body mass loss is — water gut tissue liver those those tissues shrink in response to caloric restriction — and so yeah i think most people don't appreciate the glycogen the amount of glycogen you can lose and how much water tracks with glycogen so you lose let's say you lose half your glycogen volume you take the mass of that multiply it by three to four that's the total mass that's lost given the water as well not to mention the plasma loss that comes with plasma contraction”