@mimosa1 I think that MJ works by dulling the hormones that make you feel hungry, and also slowing the passage of food through your gut so that you feel fuller for longer, and feel more full after eating small quantities. I don't think it affect the actual absorbtion of calories.
In your twin example, 'my' non-medicated twin might feel tempted by grazing on some crisps or a biscuit with a cup of tea, they might choose to have a pudding, whereas (at the moment) I'm just not interested. Ditto alcohol, which previousy would go hand in hand with a carby snack.
Of course, my alter-ego twin might manage to exert amazing self control forgoing snacks / desserts and deliberately choosing small portions. Then I'd expect them to follow the same weight trajectory as I am. For me, being on MJ makes those choices possible, even easy. My non-medicated twin might be miserable and in a battle between desire and willpower.