Some people, I believe, are insulin resistant and some are insulin sensitive. The sensitive ones tend to be skinny and have to really overeat to gain weight, while the resistant ones find it easy to gain weight.
I have dieted for years attempting to lose weight, but cutting out carbs was a game changer. Suddenly losing weight became easy. And who doesn't like an all BBQ diet?? (ok, well, even BBQ gets tiring after awhile, but I eat a variety of stuff, and even have managed to work out how to make a low carb pizza (almond meal+cheese for the crust, tastes like whole wheat).)
I do not believe all calories are the same. I eat a high fat, high calorie diet, I never worry about calories. If I'm hungry I eat. I only ever budget for carbs. So long as I'm eating meat and cheese, say, for a snack, I can eat as much as I want- and I do. (Though one of the side effects of low carb / high fat, is as your body becomes fat adapted, you find yourself hungry less often. I have on occasions simply forgotten to eat for an entire 36 hour period.)
OF course this is anecdote, and I do think that in regards to insulin sensitivity there are at least two types of people.
And in fact, that's part of my point. The monotonous "just cut out fats and eat all the pasta you want and you'll lose weight" Official Government Propaganda Diet is not working- it presumes that everyone is the same too.
Low carb may not work for everybody, I dunno. But it worked for me, spectacularly.
For the first time in my life I'm confronting the prospect of being normal sized. Skinny even.
That's going to be weird!