This is what drives me crazy. There is almost no research on determining the factors that explain why some diets work better for some people, or finding a way to predict which diets will work best for individuals so that maybe some day "trial and error" wouldn't be the only way to find the right plan. Because it really doesn't matter what works best for the "average" person if it doesn't work for you.

As an example, there is some newer research that lower carb diets work better for insulin resistant patients than traditional low calorie diets. It's only taken me 36 years to discover that it's true for me.