You can control your tobacco use. That is why Pigovian taxation is effective.
A “food desert” doesn’t account for the person who consistently orders two flavors in their tall iced coffee (usually equates to 6+ oz of simple syrup); that’s a choice — and a severe negative externality.
Risk pooling in insurance is simply an added benefit, but a less clear moral approach when the disease is not necessarily controllable by the person. Metabolic disorders exist. Tobacco disorders, not as much except conditioning and addiction.
But, it should be a focus for wellness programs so that metabolic disorders are destigmatized.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2225433/
Now, if you wish to reduce obesity because you're more interested in a person's quality adjusted life years, you absolutely do want to treat obesity (and addiction) like a disorder, because compassion and empathy is the only way you're ever going to get someone to make the long term life choices they need to get better.
Fun fact, obese people actually have lower lifetime healthcare costs than healthy people.