Before attacking people that are obese, and making jokes about taxing food to stop obesity, you need to remember that not everyone who is obese is that way because they over-eat. There are many health reasons why people are, or become obese. Keep in mind people who are obese do not pollute the air you breathe.
Your smoking infringes on the air we all breathe. I have asthma because my parents smoked while I was growing up. I will, for the rest of my life, have to use asthma medications because people around me were constantly smoking. This is a major cost to me (financially and emotionally) and to my insurance company. People who smoke around their children are setting them up for a lifetime of health problems. Smoking affects everyone, not just the smoker.
However, putting an extra tax on it doesn't make much sense to me. It's not going to stop a smoker from smoking. Putting an extra tax on liquor isn't going to stop a drinker from drinking. It will just put more money in the politicians' pockets. After all, that's what the taxes are all about anyway. More money for politics and politicians.