It just seems logical to me. They are not having regular meals and generally less to eat, they are doing much more exercise, (mainly walking but also fighting). While some of them are in better condition than the others, there should be signs of physical changes in our group. Hirano and Shizuka should see the biggest change as their cloths will becoming looser (could be fun). All the girls should see some difference (a smaller bust size, a bit off the hips) and even Takashi may loose a size (but be gaining some muscule). Alice, assuming she was already an active child, would see little difference.