I don't know how it is the UK and Australia, but in the United States, smokers have developed a pariah-like status over the years. There are all kinds of anti-smoking campaigns, city ordinances not allowing smoking within X number of feet from a building, etc. But at the same time in the US, it is politically incorrect to criticize those who are overweight and obese. Some might argue: "Second hand smoke harms other people, but it's my choice to eat what I want and this doesn't harm other people."
However, it DOES harm other people, just not in the same way as second-hand smoke.
According to a recent study, annual spending on obesity-related diseases is expected to rise by 13-16% in the US by 2030, leading to 2.6% increase in national health spending. Total medical costs associated with treatment of preventable diseases such as diabetes, hypertension, stroke, and coronary heart disease are estimated to increase by $48-66 billion a year.
That means as a fit person, my taxes will be higher and my insurance premiums will go up to fund increased health care costs associated with an increase in obesity. Also, children with fat parents are less likely to have access to healthy foods and are more likely to be overweight themselves. Other people ARE harmed by you being overweight.
But instead of a nationwide effort to promote healthy eating, there is a culture in the United States of being fat and proud of it. Facebook groups promoting concepts like "big women are beautiful" have millions of followers, and
criticism of fat people is called "hate speech". Clearly some overweight people don't want to feel guilty about their behavior choices, so they try to make others feel guilty or embarrassed for criticizing them.
Let make this perfectly clear: being fat should not be a protected class like race, gender, sexual orientation, or ethnicity. Unlike those categories, being fat is almost always a choice. Only a small percentage of people are overweight because of a legitimate medical condition like hyperthyroidism. And sure, eating disorders with psychological roots exist, but let's be honest:
most fat people are fat because of poor food choices and because they lack the willpower and motivation to exercise regularly. They just don't like to be called out on it.