I believe that Montignac used to claim that eating low carb would enable your body to arrive at the correct weight for
you. That might include weight gain. Or loss. Or allow you to change over time.
No idea if later editions of his book stopped saying this.
I'm tempted to think that our bodies do not use BMI, mirrors, aesthetics, amount of baggy skin or dress sizes to choose ideal weight. They probably use age, activity, fertility, climate, food availability/frequency, hormones and nutrition...
@Bluetit1802
Maybe your body is far happier as it is now than if you forced it to gain a few extra pounds.