Smoking is a choice 100% of the time. There are at least some instances (a small minority) where being overweight, even extremely obese, is not entirely a choice. It's apples and oranges.
You might be bedbound and not in control of your own food. But, the staff could just give you less food.
There is no medical condition that will cause someone in a locked room given a calorie restricted diet to gain weight. That is against the laws of physics.
It's fine to say "losing weight is very very very hard". But it's incorrect to say "being overweight is not a choice".
You (unless you are bedbound) choose what goes in your mouth. You, thus, have control of your own weight.
it probabbly "works".
Also is enough to get someone kicked out of office, as the public loves sugar.
Once you grant the existence of individuals that are outliers in susceptibility to addiction (which I think is reasonable because it's such a highly polygenic trait) I don't see how one could claim that obesity is sometimes not entirely a "choice", while smoking is always a "choice".