Losing weight isn’t even particularly desirable in itself. It’s a reduction in fat mass, especially visceral fat, that’s going to improve health. Gaining muscular and skeletal weight is going to improve most persons’ well-being.

The metric to target is body composition, not weight. And for that metric, there is a whole lot more than calories in or even nutrients in. Endocrine profile has a huge effect on nutrient partitioning, just to name one thing.