So, from the fact that underweight people are less healthy than neither-underweight-nor-overweight people it doesn’t follow that overweight people are also healthier than neither-underweight-nor-overweight people, and hence that there’s no good reason (other than signalling) for people to not want to be overweight, does it? (Or am I misunderstanding what the whole issue is about?)
They aren’t. That would be crazy.
So, from the fact that underweight people are less healthy than neither-underweight-nor-overweight people it doesn’t follow that overweight people are also healthier than neither-underweight-nor-overweight people, and hence that there’s no good reason (other than signalling) for people to not want to be overweight, does it? (Or am I misunderstanding what the whole issue is about?)