I always think of a part in a programme that Dr. Xand van Tulleken did -- explaining how the combination of fat plus sugar is highly addictive. Basically, try to eat a pot of cream on it's own; you can't It's too much. Same goes for sugar on it's own. However combine sugar with cream and it turns into the most addictive food-stuff on the planet. This is the basis for so much junk food/processed food and people that are used to eating that **** have just forgotten what real flavour is.Eating and drinking for pleasure, as opposed simply for just sustenance is in my opinion, combined with inactivity and poor education are the primary causes. I think sugar plays a part in all of that - but mostly in the way it's used in processed foods along combined with fat, to produce products which taste incredible, contain thousands of calories and are probably addictive, or not far off.