Yeah, you're looking at a
lifestyle change. There's no quick-fixes and instant-results in becoming healthy. It requires a long-term big-picture approach to your life overall in how you feel about yourself, how you see yourself integrating with society, what your future goals and plans will be, your level of commitment to those dreams. It can take years to make the shift from where you are now, to the kinds of activities that will lead you down the right path and even then, decades to finally achieve your results.
Part of this is watching what you eat and the other is exercise. Again, it's a big lifestyle change that's got to be encompassing as a whole, you're doing it FULL-TIME, every day, all the time. You are changing
who you are as a person 24-hrs/day, and that's where the results will come in, not what you do for 30-minutes a day. Change your attitude about yourself,
"I am a fit and healthy person", "I am a top-athlete", etc. and it will eventually soak in. When you pick up that triple-bypass cheeseburger with extra sauce, it will be contradictory to your character and you'll be grossed out. At that point, the diet-Coke won't make much of a difference
So get into it gradually, you'll want to work up to 10-hours a week of riding. Commuting is a good way to get that exercise without devoting specific times for it. In school, I use to ride the 13.5-miles to the bike-shop where I worked part-time. Then rush back for classes later. Sometimes, I'd go back & forth a couple times a day!