Other people have already got the MRE angle covered. They’re not bad tasting, but yeah, damn near a whole day’s calories in a single pack.
For getting in great shape, I’ve been doing CrossFit since the summer of 2007. I lost over 10 kg, doubled my max lifts on all exercises compared to when I was doing regular Men’s Fitness type workouts, and went from puffing like a smoker in the Himalayas after running a relatively short distances of 1–2km to being able to crank out 5k in just over 20 minutes. Check out “Start Here!” in the side bar and also read the FAQ. There are a ton of videos for exercise demonstrations and inspiration. Start easy and light. I started doing a lot of exercises with a bare bar to get used to doing the form correctly.
For diet, if you know you’re bad at portion control you have two options: prepackaged (which you thought about here) and meal planning. Prepackaged foods are more expensive than buying stuff yourself and preparing meals. Weight Watchers meals are often recommended as being decent and not horribly expensive. Stay away from non-diet prepackaged stuff like TV dinners, even if they say they’re “healthy” because usually they are most definitely not.
Option two is planning out your meals, with or without the aid of a diet framework. I personally eat Zone-ish without any strict planning, food was never my problem; inactivity was. Zone proportions are roughly 40% carbs (mostly vegetables, few starches) 40% protein (lots of chicken, no skin, fish, limited amounts of lean cuts of pork and beef), and roughly 20% fat from your protein sources, oils, and some nuts.
Zone gives you good rules of thumb for estimating portions, and encourages you to spend at least the first two weeks weighing stuff so that you know what a real portion looks like. You also eat about 6 meals a day, so you don’t ever really get hungry, even though your actual meals are pretty small. Paleo, also known as the caveman diet or neolithic diet, is another option for losing weight while doing heavy training.
Either Zone or Paleo accomplishes weight loss essentially through: portion control, recommendations that specify high-quality foods that would be difficult to gain weight on unless you gorge, and meal timing. Those are all things you could do on your own if you wanted to spend the time researching foods and recipes, but it’s obviously easier if you follow diet plans since they’ve done the work for you. There’s free information on both Zone and Paleo/Neolithic diets out there so you don’t even have to buy a book unless you want to.
Since you know you’re prone to impulse eating, you’ll have the best success by planning out meals. Do your shopping for a week. Know what you’re going to be eating for the next day. Plan it out. Make your meals ahead of time if possible so that you’ve got stuff ready when you’re hungry. That means you’ll have good food available so you don’t hog out on junk food or whatever.
You’ve got a lot of work ahead of you. Be patient, keep plugging away at it. I only had about 15 kg to lose at my fattest and it took me about four months to see real results, and about a year to get down to low teens in body fat. You’ve got a lot more than that to lose, so don’t get discouraged. Good luck, man.