It’s as simple as this.
Typically when people object to doing gym they seem to read from a script and say “they don’t want to do weights and get too bulky”. But when you look at images like this you can clearly see how if you swap fat for muscle you MUST reduce volume. While the weight in the scale may stay the same or even increase your volume and therefore size gets smaller.
Muscle takes up less volume than fat. If you’re smooth rather than ripped, it camouflages your muscles as well.