I'd've rated Adipotide at 2 (make a large difference to the lives of hundreds of millions of people), and even with cognitive effects factored in, well, Apple hasn't had zero cognitive effect either. The thing is, there was already an age before high-fructose corn syrup when almost nobody was obese - you couldn't call it a novel change in the human condition to put things back to how they used to be. If you consider Apple as having popularized icon-based GUIs then it's got a substantially better claim to 5 or even 6 than a completely effective anti-obesity drug.