Why is protein emphasised during weight loss?

Weight loss removes some lean tissue as well as fat, and protein intake is discussed alongside resistance training as the pair of things associated with preserving more of it. The emphasis grows when appetite is reduced, because total intake falls and protein can fall furthest.

General healthy-eating guidance covers protein sources across animal and plant foods and is written for the population rather than for someone on a specific treatment. That is the right starting point but not the end of the question.

How much protein suits you depends on your kidney function, your other conditions and what you are being treated for, and there are situations where higher intake is specifically not advised. That makes it a question for a clinician or a registered dietitian rather than a general number from a page like this.