Being fat is unhealthy. You can live a long time in spite of that, but it’s unhealthy. Smoking cigarettes is unhealthy too. I wasn’t aware that this was a controversial thing to say.
If you are disease-free and your body can perform daily activities normally you are healthy, weather you are fat or skinny, smoke or not.
No, if you are 400 pounds, you are significantly less healthy than you should be. Disease-free or not.