I've lost over 100lbs in the past year.
* I only eat one meal a day (supper). It's usually a very large meal, very high in lean protein.
* I avoid sugars and starches of all kinds and minimize other carbs (fruit, root veg, grains).
* After eating, I do 30 minutes on the treadmill.
For a middle-aged woman (a category which finds it particularly hard to lose weight) this has worked rather well. I can eat as much meat, (non-root) veg, dairy and soy as I want and I just keep losing weight.
So no, calorie restriction isn't the 'only way'.
What you've described is calorie restriction.
You restrict calories to one meal where you can't possibly eat 2000 calories at once with the ingredients.
Exercise + starting off at a high weight helps further.
How do you know that spreading that one meal out throughout the day wouldn't have the same effect? I bet you'd have more energy as well.
Unless you have tested this, I find it hard to believe that this isn't really just a caloric deficit compared to whatever you were doing before losing weight, assuming the same activity level.
What you describe in your diet is significant calorie restriction...
isn't one meal a day another form of calorie restriction though?
It's very difficult to not be in a calorie deficit when you only eat once a day and are consistently active.