Hmm, I'm not sure if the items in the background matter so much, but you should strive for the same lighting, camera, camera locations and poses.
If you can use the same precise setup over a period of years, that might be nice, but large changes will certainly be readily apparent anyway.
Anyway, sounds like you have a good plan, it should certainly be achievable as while you are very overweight you can lose weight at a relatively quick pace at first.
Whatever you do, don't be discouraged by the odd setback, just keep on working and you'll keep on improving... and the more time goes by that you haven't fallen off track the more pride you'll take in your journey.
Go get it!