When it comes down to it, the only thing that really matters is the number of calories you eat vs the number of calories you burn. It really doesn't even matter if you eat healthy or eat pre-processed crap.
A recent study was done nicknamed the "Twinkie Diet" or the "Convenience Store Diet" in which the participants in the study were only allowed to eat what they could find in a typical convenience store, including snack cakes, beef jerky, sodas, whatever, though they also were allowed (encouraged!) to also make use of the protein shakes you can buy there. The only other rule was a strict calorie limit, different for each person according to their height/weight/sex/weight loss needs, 1200 to 1800 calories per person.
At the end of the 6-month study, the participants lost an average of 30 pounds.
The study stresses that this is NOT a healthy diet. It only proved that weight loss is in no way dependant on *quality of foods* eaten by the person who wants to lose weight.
That said, I've lost nearly 100 pounds in the last year, using CICO (calories in, calories out) and I found I lose weight faster when I reduced carbs of ALL KINDS (no such thing as a good carb!) to about 20 percent of my diet, and eat a diet high protein and fat, limiting myself to 1500 calories per day. I eat mostly meat and vegetables, with regularly scheduled treats, such as a chocolate truffle or a danish or a bowl of cereal. Fruit is REALLY high in carbs/sugar, and is reserved for a treat. On an average day I eat cheesecake for breakfast, bacon wrapped chicken and a cupcake for lunch, and pork with stir fry (a mix of cabbage, mushrooms, broccoli, cauliflower, squash or whatever I have) cooked in butter.
There are two keys to this diet. 1) measure *everything* to the ounce. Don't ever try to guess, and don't ever assume the package is right about how much a single item weighs (especially with sausages or hamburgers or slices of bread, it's usually wrong!). Weigh it yourself. 2) Do not eat ANYTHING unless it's already been weighed and logged. And once you're out of calories, that's it. Nothing more, no matter how hungry you are or how loudly that last chocolate cupcake is calling your name. It's about self-control.
And it's forever. The moment you stop "dieting" you will gain the weight right back. You don't have to stay on the lower calories limit, but you pretty much have to count calories the rest of your life. Eventually you start to learn how many calories you can eat eyeballing it, but you need to monitor your weight at least weekly, to make sure it doesn't creep up without you noticing again.