it's sugars and carbs from starches and high fructose corn syrup.
Those extra carbs spike blood sugar and the body starts storing more and more fat in fat cells.
Higher protein (and, yes, even eating protein-laden food high in fat) is the best thing for a human being. It's what we ate for millennia. All this processed crap and chemically altered crap and highly processed wheat is a rather recent introduction into the human diet and it's literally killing us.