The problem with obesity and all related problems caused by the increasingly sedentary lifestyle of our post-industrial societies is that it is difficult for a lot of people to find the motivation to do it, and then have the discipline to keep with it. But what if the government paid everyone to do it? All the government would have to do is throw up/purchase a number of buildings that don't need to be much more than one large room which they throw enough basic excercise equipment into. It then sets up a program where every day you are able to go there at certain times to participate in a guided workout for 45 minutes. Whenever you show up you sign a form or swipe an ID card which will then entitle you to that day's payment on your tax return. The pay would be $5 for kids(they don't need a lot of money to be motivated, hell, they are mostly willign to do this anyways), $10 for teenagers(again, an already fairly active bunch that will appreciate the sum quite a lot), and $25 for those 19+(because you are an adult when you have all your rights and $25 is enough to make it wiorthwhile to maybe miss that one hour of extra work. Everyone will be able to attend this once a day and every day of the week.
And if you think this will be too expensive, think about how much money the government reduces its revenues by whenever it makes even a 1% tax reduction. And the initial start-up costs can come out of some of the money that will be saved in healthcare spending from the marked increase in general health and well being of the populace. The government of the future will encourage the development and happiness of its people. It is time that something truly beneficial to the whole of society is legislated.