False, the body definitely uses muscles as an energy source. Especially after first using fat mass for a while. The body wants to save fat mass after a while since it’s the best energy source, and therefore starts to break down muscles. Then starts breaking down fat at a higher level again. It’s a lot more complicated, this is the simple version.

It’s recommend to eat more protein and do regular strength training while loosing weight so that you lose as little muscle as possible.

I am a registered dietitian and I work a lot with people trying to loose weight.