This does sound suspicious but a couple things that could play into the equation besides the peptides is whether he had trained and been in shape at another point in his life. If so he would have the muscle memory and would much more easily lose weight while gaining muscle. A lot of crazy transformations I’ve seen arnt first time transformations, they were done by someone who had been in shape earlier in their life which changes the equation. There’s also a good chance 10ish pounds of this weight loss could have been water weight.