It's all about doing what our intellectual and moral superiors want us to do.
First our intellectual betters provide us with information to make better (that is, choices they'd like other people to make) choices.
When that doesn't achieve results, they pass laws to incentivize us to make better choices.
Then they try to stigmatize people who still don't make better choices.
Finally, they just order people to make better choices, because it is so much easier, will get better results, and because our intellectual and moral superiors will be the ones doing the ordering and it really is for our own good.
We've reached step 3 on the weight issue.