19 year olds have lots of energy!
I have to agree that working in a grocery store could be an asset to you! You are 19 and will not be living at home forever (we hope!) I bet once your family sees you walking and eating salads- or whatever- they will start to look at their own habits! Especially as you get thinner and fitter! Plopping down at the family table to eat mac n cheese every night might be the lazy/easy way to go, but where has it gotten you so far? You gotta start packin' your own lunches, whippin' your own simple dinners up, having healthy breakfast stuff around you can grab.
Think about one or two of your thin or fit friends for an example. What would they eat in one day? What would they DO in one day? At 19 I rode a bike to college and walked the campus with a back pack. I worked swing shift in a warehouse or waited tables. At 19 you can be as active as you want to be for the most part. The more you find ways to move, the more lee-way you will have with what you eat. I can't stress activity enough. I never thought the gym was all that fun, actually. I would rather jog, bike, skate, ski, hike, or ANYTHING else besides go to a gym. I worked in them for years, too. Walking is free and you can do it anytime. A leisurely stroll is not what you want. You want to do a warm up- like 3-5 minutes, then walk hard/ walk mellow/ walk hard/ walk mellow/ with a plan to work up to a good one hour of "walk hard". Maybe first you only get 10 mins in. Try to go up a hill and down a hill, if you can. Go every day! As the weight comes off, you can start really slow jogging. That's how it goes. One day at a time!