Lazy described me to a T. All of my interests centered around activities that required little or no movement, and my eating habits had degenerated to pre-prepared frozen meals and fast food restaurants (faster, less work, no dishes). I had never in my life been an active person- even as a child I spent the vast majority of my time reading and studying.
I just decided that I was no longer going to be that person. Instead, I would be an active, even "sporty" person, take up cooking as a hobby and start engaging in a lot of different activities. It was a 100% mental change, and really was amazingly easy to make (I guess I was ready for it). Then I just followed up that change with the actions that were needed, each day, every day.
It feels strange that, after all of my life defining myself as lazy, I find that I really do enjoy this new lifestyle. I never suffer from boredom, because I have so many more things I can do "when there is nothing to do", and the food I get to eat at home is restaurant quality without the cost. My health has improved greatly in several ways, not just my weight- and of course that has improved greatly as well.
My advice, from one lazy person to another: look for enjoyable forms of exercise, don't try to force yourself into a routine. Don't just "cook food", cook excellent meals. I find that the extra immediate reward of enjoyment is needed to keep us from falling back into our old patterns of (non)behavior. Be strict, but flexible with your plan, and focus on behaviors and not their outcomes.
Good luck!