Or we could encourage healthier lifestyles. A good start would be introducing requirements for pedestrian footpaths and bike lanes in new communities. Trying to walk or ride a bike in many recently built communities is either impossible or scary.
That's just one idea, there's a lot of others out there. The bottom line is that if we sit on our butts all day and eat high-caloric sugary foods, then we're going to get fat. That's simply the way our biology is wired. I have a hard time imagining that any new wonder-drug is going to change those fundamentals.