Personally, I drink soda maybe once every 2 weeks and I almost never eat candy. I try to do pushups, situps, pullups, and 30 minutes on my punching bag at least 4 times a week. This keeps me fairly toned, you could try that.
This summer I have a lot of time on my hands, since my job starts at noon, so I'm going to start running hard and working out (lifting weights) daily in the mornings.
Edit:
Also for motivation:
"Whether you think you can, or think you can't, you're right." - Henry Ford
Don't let people look at you and use you as a benchmark for their progress. Don't fail yourself, and don't end up like I used to be where I'd mention I wanted to work out and people would laugh. It's not a good feeling.