I shouldn't have said "for every study another contradicts it" because that's probably a little extreme. I wouldn't be surprised if there were some pro-sugar studies published in the 70s, but I haven't read any current studies that claim more sugar is better. It seems fairly obvious to single out things like man-made trans fats and sugar extracts like HFCS that do not commonly occur in nature. But the studies I like to read are the ones that conclude that carbs are good, that carbs are bad, that fat is good, that fat is bad, etc. One thing that seems to converge is that most doctors that push a certain diet have made it their career. So if they were proven wrong, their name would be mud. For example, Dr McGregor, pusher of a vegan diet who is known for cherry-picking data, makes income from his website and books. Dr Esselstyn claims that ALL fat and oil is bad and sells books. Meanwhile Dr Atkins sold books stating that fat is good and carbs are bad. Eskimos lived off of meat and fat and barely any carbs and plants. Meanwhile other ancient civilizations thrived on carbs such as corn, rice, and potatoes, but didn't have a lot of access to meat.

That's why I like to read these nutritional studies. All we've proven is that we don't know what is best for us, but we can prove that any method works in a controlled study!