I ate super-clean, super-healthy for two years and lost nada. I stuck at 150lbs the whole time. Pissed me off. I was also on Zone at this point, still ate oats and tofu, so not really primal.
I did Atkins for a year, lost nothing.
I basically didn't lose weight period until I started counting calories. It's just my experience, others may differ, but imo, THE deciding factor is calories in, calories out.
Granted, I think that eating primal- lower carbs, getting rid of stuff that's easy to overeat like grains, sugars, etc- helps a lot.
But honestly, I think you could eat a high carb low fat vegan diet, about as far from primal as you can get, and STILL lose weight. Just as long as you were eating less calories than you burn.
Just IMO. Some people may be able to get their calories down without counting, but I do like to count, these days. I like being 120lbs and wanna stay there. That means my ass eats 1700kcal on days I don't exercise, 1900kcal when I do. And not a hell of a lot more under any circumstances, really. The weight has stayed off for two years now.
Getting my Grok on in the Pacific Northwest.
"C is for cookie, that's good enough for me."
"Cookie is a sometimes food."
"Sometimes cookie monster eat APPLE instead of COOKIE. Sometimes eat CARROT."
-Cookie Monster, partially reformed sugarholic