You can complicate the concepts of weight gain and loss all you like, it always boils down to calories in Vs calories out.
You’ll show me 99 people that have several excuses about why they in particular can’t lose weight and I’ll only be able to show you one that holds their hands up and says “I admit it, I’m weak and I’d rather have cake now than a nice body a few months later”.
Losing weight is like stopping smoking, it’s all conjecture and day dreams until one day you say “fuck this, I’m changing and sticking with it STARTING NOW”.
Some people need tough love, not more readymade excuses.