healthcare - fat tax based on BMI

I am writing an essay on implimenting a fat tax based on BMI levels. i need help with discussing whether it would be equitable and efficient to price descriminate based on BMI (charge higher prices to indivituals with higher BMIs) in this i need to discuss adverse selection, the economics of health insurance, and specific connections to price descrimintion)..any help in detailing this out would be much apprciated. this is my last section before the conclusion and i think i have hit a block...