Everyone has already given you words of encouragement that I would have so I'll just pipe in with some CHEAP and healthy food alternatives, along with some math to show you how you can get started at least. My suggestion is this, since right now you have very little choice in what food is in the house, what you do have a choice in is portion size and there are a couple of alternatives of "get full" snacks on pennies that are also healthy.
First and foremost, barring any health or metabolic problems you have, it should be fairly easy to drop a few pounds just by making some small changes. Here is the simple math:
At 400 pounds and 6 feet tall, you need to consume 3277 calories every day to stay that same weight. If you were to cut down your daily intake to 2777 per day, you would lose 1 pound a week. Cutting down to 2277 per day would be 2 pounds a week. (You get this number by taking 3500 [which is 1 pound of fat loss per week], divide that by 7 days, and you get 500 calories per day you should avoid.)
Now, how to do that?
Step 1 is figure out how many calories per day you are really and truly eating. You need blunt honesty with yourself (no one else needs to see your food log). You need measuring cups or a food scale, and you need to face the truth. If you aren't honest in figuring out how many calories in have in a normal bowl of pasta, then you won't know how much pasta to cut down on. Take a few days and write down every single morsel and the amount you put in your mouth. Once you have that data, you have your baseline on where you can cut down.
500 calories a day is as "easy" as skipping 3 pieces of bread when you normally would have had them, OR taking 1 c. less pasta, OR 1/2 c. less pasta sauce. As you learn how many calories are in the foods you eat, it will be easier and more obvious to you what you can avoid.
As far as cheap, healthy filler foods, the best thing I just discovered is sprouting beans! You can eat a metric frakton of sprouts for so few calories its ridiculous... like tummy ache full. And it costs pennies to sprout beans. You can use the regular beans from the grocery store or order them online (garbonzo/check peas, peas, lentils, mung beans, adzuki beans). I use an empty pickle jar, a cloth and a rubber band as my sprouting vessel (no need to spend money on fancy contraptions they advertise online). Here is a very down to earth, no-nonsense intstructable on sprouting
http://www.instructables.com/id/Spro...r-own-Sprouts/
I actually like to eat these at about the 3rd day when they are still bean shaped and just starting to sprout. They are crunchy and more of a snack of a vegetable then a salad item (I really don't like salad...). Anyway, this might not appeal to you so I'll stop blathering. I can say a lot more / give more information if you are interested. Just let me know.
Some other easy changes to get you started:
- use 1 tablespoon of butter instead of 2-3 in recipes / your pans
- drink a big glass of water between you first and second serving (you might get a little fuller and maybe not take as much on the second serving)
- switch some of your drinks to diet
- switch out 1 soda a day with 1 glass of water instead
- add water to pasta sauces so you end up having the same amount, but you have cut the calories a bit
- see if you can get the family to switch to a lower % milk
- get skim mozzarella cheese - taste and acts exactly the same as regular mozzarella but is 3/4 the calories of regular.
- eat on smaller plates (this sounds stupid, but my brain feels fuller when I eat a huge mound of food off a small plate than when I put the same amount of food on a regular size plate and it looks like a small little portion)
And finally, there is always getting a little extra exercise, but I know that might be out of the question. When I weighed 332 (and much shorter than you...), going a block extra was excruciating on many levels. But every little thing you can do when you are in a situation where you can't change the food in the house will help.
Just start small. Maybe you will only lose 10 pounds... but that's 10 pounds and you will feel better. Worry about the big picture later, and just focus on what small changes you can make for now in the situation you are currently in.
Sorry this is so long.
Hugs.