It's worth it when you think of the consequences of an unhealthy lifestyle as you get older. I was a fucking pig until two years ago. I stand 5' 9" and two years ago I weighed a fat 212. I started riding a bike to work and lost 40 pounds in 3 months.
I can honestly tell you it is a world of difference. But when I really noticed a change was when I quit eating fried foods completely and switched to just grilled meats and salmon steaks. My energy levels are off the charts. When I was overweight, I'd break a sweat just doing minimal tasks, but now I don't do that.
Diet is key, you can jog all day and lose weight, but if you want to BE healthy, cut out the shit you put in your mouth and arteries.
EDIT: I'd also like to add that I forced, literally forced myself to substitute water for cola. You'd be surprised what those 12 oz. cans of sugar can do to compromise a diet. Changing my diet was actually harder than getting up to run in the mornings. Especially when everyone around you is chowing down on delicious pizza. It won't happen overnight, but breaking bad habits feels great mentally, and that's what keeps me doing it.