I just rounded this weekend and took care of a very unfortunate 38 year old woman weighing 598 pounds after having part of her pannus removed (that large part of her pendulous lower abdomen) and a portion of her foot amputated. She could no longer observe her feet and developed an infection of the bone there. Taxation of soft drinks would not have prevented this unfortunate situation. Rather a serious look at the psychosocial dynamics of her family who acted as co-dependents to her problem (she hadn't left her house for three years) might have been more effective.
What about filming a few unfortunate obese soles who are agreeable to tell their stories so others can learn from this experience and stand them next to their skinny children, similar in emphasis like the former antismoking ads like the Marlboro ads of the sixties or like this:
Taxing the entire populace to thwart the few won't work. We all have a responsibility to educate our kids about nutrition and health.
And what will these taxes be used for? Probably to support the AMA's sagging physician membership fees. Like mine.