I am very overweight (Obese). At one point up over 330lbs at 6'2". I'm not the stereotypical fat kid with a pantry full of twinkies and who eats fried food all the time. In fact, I hate fast food. I love salads, love fruits and veggies, and prefer lean meats. My diet wasn't bad (portions were big) but I was completely sedentary. Office job, the whole 9 yards. Just didn't get much activity. Reducing portions (but pretty much eating the same foods; cutting out only a few things), and beginning to exercise has me down now close to 40 lbs, and falling.
You lose weight when you use more calories than you take in. Period. That's it! Either eat less,or exercise more. Also, don't guess. Measure, and look. I was amazed that some of the foods I'd eat that I thought were healthy, are FULL of calories. Sometimes they sneak it in on you. Like a small, snack size bag of nuts that says it had 4 servings in it. But of course you'll eat the whole bag; which is a ton of calories!
You need to measure your food, and look at the calories. And you just need to exercise.
I live in a very rural area. You realize the role activity plays in weight loss living here. When you see a farmer who has 3 or 4 eggs, bacon, sausage, and toast (and no, not egg whites or wheat toast) for breakfast, loads up on a couple burgers for lunch and scarfs down steak, a baked potato, and a salad covered in the mornings bacon grease (yes, it's still a common thing out here to make salad dressing out of bacon grease; don't waste anything!), and is thin as a bean pole; you'll realize it. These guys burn thousands of calories during the day in the work that they do. Same with the folks who board horses, work construction, or do all sorts of other jobs where they are working hard, physical jobs 8+ hours a day. (Usually a lot more than 8 hours a day). And here I am skipping breakfast, eating a light lunch, and having a nice dinner at night with my wife. But I'm not doing anything, so it's all being turned into fat!
And again, you've gotta check! I like chicken. I almost always have some lean, boneless skinless chicken breasts in the freezer. Healthy right? Sure, unless you're like I used to be and you'll have 2 or 3 of them as a meal along with a side. One is plenty, with some fresh greens and another healthy low cal side! Heck, Subway, the famous healthy Sandwich! Get a 12" with extra meat, load it with dressings, and you'd have been better off to have a Big Mac! (For the record, chopped salads; basically a Sub without the bread chopped and in a bowl, are an awesome low-cal low-carb choice at Subway)
Good luck to you! But the bottom line is, less calories go in than are used. That's how you lose weight, period. Athletes eat thousands of calories a day. Think I read somewhere that some baseball player eats 200% the recommended amount of carbs per day and around 6000 calories. Well; when you work out all day every day you can! In fact, you need to!