I mean when I needed to lose weight (15kg, 85kg -> 70kg) I started with calorie restriction, and as a result of that actually looked at what I was eating and realized I was incredibly low on protein, and then from that added some daily light exercise partly just to avoid getting bored and wanting food.
So this isn't really 3 separate unrelated changes. Also at least in my experience, people tend to regard high protein things as the "energy dense" part of a meal - the problem with a lot of carbohydrates is they're not very filling.
The biggest problem with exercise is it's an awful way to lose weight - you don't burn that many calories, it makes you hungrier, and then your body optimizes to burn even less calories as you do it.