I watched my husband pack on the pounds for 10 years of our marriage, he would lose weight, then gain it back, and he suffered from horrible headaches. Then on accident he discovered he is sensitive to gluten. When he stopped eating bread, pasta, cereal and all things made with wheat he lost over 60lbs; he went from a size 38 to a 32 in less then a year and now the 32 is almost to big. He did not exercise and the pounds just melted away by changing his diet. I am not saying you may have a sensitivity to gluten I am only pointing out that the permanent diet change caused my husband to lose weight. Anyway I prepare all our meals from scratch my husband only eats vegetables, fruits and proteins. He takes his lunch to work usually leftovers, if we don't have any leftovers he will take vegetables and lunch meat.
Soup is easy to make on the weekend or whenever you have time and then use it for lunch through the week. Beans and rice, brown rice is healthier is a good meal you can add some cheese, lettuce and sour cream to make it more interesting. I also make a lot of stir fry type meals, heavy on the veggies and a little meat goes a long way in a stir fry again over brown rice. Casseroles are easy to make and save well.
For snacks look to carrots, celery, apples, air popped popcorn they transport easily and you have to chew them a lot so you feel like your eating more. Add some protein to your snacks cheese, peanut butter, hummus within serving size are all good choices. Stay away from gateway foods like chips, pretzels, cookies the things that are hard to eat just one of. As for fat free and low fat dairy we do not eat low fat anything in our house the lower the fat the more processed it is. Your body needs some fat to function properly, we just eat in moderation and stay away from hydrogenated fats, and mono and di-glycerides. Drink lots of water. Once you get used to making your own meals you will find the processed food you once liked no longer tastes good, and is incredibly artificial tasting and salty. Good luck.