My question to you in response (which sounds a lot more insulting and a lot less complicated at first glance than it actually is):
Is it really about you?
Let's think for a second about what governments do and how regulations relate to those things-
Governments put in a lot of money for roads, education, social security (generically speaking, from the SSA to homeless shelters), healthcare, national defense, water infrastructure, law enforcement, and innumerable other necessary (along with other, admittedly unnecessary) services and capital projects.
All of this is paid for by tax revenues; not just your taxes, but mine and everyone else's as well. When someone doesn't wear a seatbelt and get into a car crash, it's the rest of us who pay a public employee to scrape their brains off the pavement. When someone sends their child to school, chances are that it's paid for by a large number of other people. And when someone commits a crime, it's taxpayers who provide the police that respond, detectives that investigate, the judicial system that tries suspects, and the jails that hold the convicted. Subsequently, governments require the wearing of seatbelts, dictate educational policy, and regulate law enforcement.
Obesity falls under the same heading of public costs because of its effects on public health; taxpayers have to pay more to take care of every obese individual if and when they use medicare or medicaid, health insurance policy holders (both individuals and businesses) pay more for the added expense incurred by each obese person enrolled with the same company, and the entire economy suffers from the decrease in productivity that comes with an unhealthy workforce, hurting the entire constituency of the federal government.
In any case, obesity- especially on the scale in which it appears in this country- costs everyone something, and we can all either pay to allow people to be as self-destructive as they will on their own, or the public sector can try to reduce obesity at the expense of some personal freedom.
It's a matter of balance; you just need to choose your priorities.