This wouldn't be such a big issue if people would stop feeling entitled to become involved in other people's business. Also, if people would start being more confident in themselves and stop being subconsciously convinced that treating other people with disrespect somehow makes them superior by contrast. It doesn't. Really.
Everyone should just mind their own businesses about these kinds of things. You could argue that they raise taxes because of medical costs (in countries that provide free health care to all residents, even overweight/obese citizens whose conditions may have been provoked by being heavier), but then that's actually more of a sociological problem than anything. Someone said for every 1$ invested in preventive health care, you would gain 4$ back on reduced medical fees nation-wide (learned this in Anthropology 12U). That's the kind of paradigm shift our generation needs: prevention, not post-issue resolution.
Which just takes us back to how really, it's none of anyone's business, and if someone is concerned about taxes (because they're paying for larger people's surgeries / medication through their tax dollars, which therefore affects them inadvertently), rave the government for not investing in preventive care. Riot because there aren't enough free weight loss resources / clinics / gyms. Get them to get junk food and beer off of TV, incl. fast food ads, and replace them with good foods and their benefits. Ban fast food in major retailors i.e. Walmart which hosts MacDonald's, or legislate that the menu must consist of at least 50% low-fat, low-sugar foods as per a nation standard.
That kind of stuff.