My wife lost 80 pounds when she increased her caloric intake but changed things in her diet and did this in a very short period of time with no suffering and no increase in her physical activity. She definitely was not doing enough to warrant an intake of 2300 plus calories a day and yet... the weight vanished.
She has maintained that loss for well a year and has not changed her diet.
What the CI/CO and folks who subscribe to the first law of thermodynamics fail to realize or refuse to admit that humans are far more complex physiologically, that different foods have different effects (it is those darn hormones), and that 1000 calories of protein, fat, or carbs are not equal to each other.
Processing them requires different energy input, they trigger different hormones, and building a better engine can go a long ways to becoming more metabolically efficient.
Weight loss may not be as much a result of restricting calories when you are being active or more active as you are building more lean mass (even if you can't see it) but if you are restricting calories you will also be limiting your activity and slowing that process of building lean mass.
Extra fat does not get turned into muscles, it just gets converted into ketones and is either metabolized or flushed.
Protein can be turned into glucose when it is required.
If we simply look at the macros and our energy needs, the only food we need is protein as it can do it all but that would not be good... the health benefits of fats in the diet are far reaching, and a small amount of carbohydrates can provide massive amounts of nutrients if they happen to be green or brightly coloured vegetables and fruit. The effects of a high protein diet are not sustainable in the long term as processing protein puts a lot of stress on the body.
Calorie restriction is a short term fix to a greater underlying problem which is not just eating too much but not eating well.
Harvard did a study on weight loss where the disparate test groups were all put on a calorie restricted diet but one group got to eat 300 more calories while limiting carbohydrates... they lost more a lot more weight than the other groups.