Letting hunger go to zero and health fall a bit before eating (but be careful, I've died of anorexia a couple times when not paying attention) and working out at the gym daily has worked for me, but it does take a while, at least a month if I remember correctly for a drop in BMI of 1. This was in previous versions, haven't played 5.1 much yet.
It is definitely too slow, and it's easy to become fatter.
I locked it with the ring at 21.
It would take too long to drop it further.
I would prefer for the ring to be more powerful, and not just to drop a single cm of height, for example. I mean, you've gone to the bar all day, you've seduced 10 different men, you've convinced them to not use any condom, you've performed anal sex (that you don't like)...all to lose just a cm of height?
I don't know what comes after the 2nd time you charge the bracelet, but it looks way too "grindy" to me