I saw where Stephan had a big post about carbohydrates the other day that garnered many comments. I think the substance of the post, that carbohydrates as a macronutrient class are not to blame for obesity, is correct, and I have written before along the same lines. However, this leads to confusion for some people who were pinning their hopes of low-carb: if not low-carb, then what now?
It's almost to the point where there is too much analysis going on with this. Instead, you could look at things very simply. The infamous Pima Indians back in the 1800s were healthy on a high-carb diet. Then they switched to government rations and consumed large amounts of sugar, flour, and oil. Obesity developed. So in a simple sense, you know that you have the villian as one of these three items (or a combination of the three). This was back before there were any modern co-founders: fast food, air conditioning, pollution, baby formula, etc.
So instead of a person asking what to eat, it may be simpler to ask what not to eat. Given that various cultures have consumed different ratios of protein, fat, and carbs, there doesn't need to be much control there.
The obvious candidate for elimination is sugar (including artificial sugar). Robert Lustig is building quite a case, as has the researchers who followed before him like Yudkin. How many people have cut out sugar and not lost weight? Not too many I imagine.
So before people begin diving into the details of leptin resistance, insulin resistance, etc., I feel the basics are starting to get overlooked: a basic step towards metabolic health is cutting out the sugar. (I should specify that I'm talking about cutting sugar but not within the context of a carbohyrate-restricted diet.)