The authors wanted to compare low-fat vs. low-carb diets, but they also wanted to study genetic and physical makeups that purportedly (their word) could influence how effective each type of diet will be for people. Previous studies had suggested that a difference in a particular genetic sequence could mean that certain people will do better with a low-fat diet. Other studies had suggested that insulin sensitivity may mean that certain people will do better with a low-carb diet.
Sure, there's your one friend who swears by the Taco Cleanse. And that other friend who ate nothing but broccoli soup for a month and dropped 20 pounds, found the love of her life, and got promoted at work. But before you start blending 80 stalks of broccoli into a cup or crunching your way through a crate of tacos, check out which diets are backed by science. Because don't you want to try one that will do the trick for you?