The diet itself seems almost irrelevant. Just the simple act of paying attention to what you eat (counting calories is an excellent starting point) will help more than anything, as you'll more easily recognize poor trends in your food choices, and the awareness will encourage you to diversify your diet.
The Whole 30 lets you have as much fat, meat and calories as you want. I plowed through eggs, homemade mayo, meat, and other calorie dense food. I'm skinny enough that I don't have much weight to lose. Even so, I dropped ten pounds effortlessly.
I don't know if this generalizes to other people and their physiques, but it was enough to convince me that sugar/simple carbs really do correlate more directly to my waistline than just counting calories does. I'm sure what the right metric to pay attention to is. My hunch is that it's glycemic load.
Either way, I cut down on my sugar and carbs since then, and I've lost of a lot of the middle-aged Dad belly I was starting to develop. I don't count calories at all. It seems to work for me.
Fats are a lot more satiating than carbohydrates (ie, sugars) - I could easily put away 4000 calories of goldfish crackers in an evening, but I would be insanely full, uncomfortable, and possibly even sick if I tried to eat 4000 calories of proteins or fats. My go-to craving-killer snack is peanuts - they're high calorie on the label, but a handful of them takes the edge off my craving in a way that chips and crackers and candy don't.
I'm claiming that the set of dietary rules I chose which are based around limiting sugar and simple carbs have an end result of some weight loss. Whether that's a direct property of lowering sugar, or an emergent property caused by that is a good question, but one I don't need to have an answer for if the rules happen to work.
For what it's worth, my rules are roughly:
* No sweets unless I am socializing or it is a dessert I prepared from scratch. "Sweet" means roughly candy or dessert.
* No beer unless socializing.
* Minimize carb-heavy snacks like crackers and chips.
The last rule is fuzzier than I'd like, but I'm still dialing it in.
These rules may seem a little arbitrary, but they work for me and I find they do a good job of improving my overall diet without subjecting me to the real annoyances of rigid diets that make you do things like ask a waiter to bring you a burger without a bun, or not eat a curry that has a teaspoon of sugar in it.
Oh, I'm definitely not trying to do that. I try to have a good amount of fruits, vegetables, nuts and dairy. Basically your classic "balanced" diet, just lower on sugar and highly-processed grains.