How is a tax on sugar beyond someone's control? It just means the price of a can of Coca Cola would go up a little bit. Everyone has the ability to choose whether or not to buy a sugar drink, and sugar drinks are said by experts to be one of the leading causes of obesity and type 2 adult onset diabetes.
Regarding higher healthcare costs for those with body fat percentages over 30% (not BMI, actual measured body fat estimate), its simply about paying more for statistically using more with regard to insurance. Is it fair to make a 16 year old boy in a Camaro SS pay more for car insurance than a 45 year old man in a Camry LE? I would argue yes, because the insurance costs for the former are certainly higher than the latter on average, even though no one has control over their age. Ultimately though, when you set rules, they have to be for the 99.9%, as otherwise you can name rare exceptions for just about anything.
I agree with the principle, but don't agree with the way. Agree to disagree. You HAVE to have exemptions. "The needs of the one outweigh the needs of the many".