Here’s a new study looking at the correlation between carbohydrate consumption and obesity: “Macronutrients and Obesity: Revisiting the Calories in, Calories out Framework.” The study looked at how changes in the amount of calories coming from carbs from 1974-2006 in the US and in various other countries in the last decade correlate with obesity levels. Basically, the more calories people get from carbs, the fatter they get. This tends to be because when people eat more carbs, they eat more calories.
This seems consistent with other research. The A to Z Diet Study showed more weight loss with people on a high-fat diet than with other alternatives. This study on weight maintenance also showed better weight maintenance on a high-fat diet than with a high carb diets. I’m not aware of any contrary research on this. The general consensus is that high-fat diets tend to be better for appetite management, which is the bedrock for any successful diet that we weak-willed, flesh-and-blood humans might try to stick to.
That being said, even if high-fat diets are better for weight loss, whether it’s healthier overall is a whole separate and much more controversial question.