Healthy foods (e.g. fresh fruit and vegetables) being more expensive than unhealthy ones (e.g. McDonald's) is one of the structural incentives causing increased obesity in the US. In most countries - including Europe - it's the opposite way around. You're quite right to say that people should take care of their own health, but if you live in a place where cycle lanes will get you everywhere you need to go, there are plentiful public green spaces and healthy food is cheap and available everywhere (as I do in Germany), then staying healthy is a lot easier than if you live in, say, the suburbs of Houston.