Over the last two decades scientists were starting to raise concerns about obesity and looking at the reasons people become fat (e.g. fat intake, sugar intake, exercise), but under significant pressure/lobbying from food corporations the focus of attention was pushed away from sugar intake and onto to lack of exercise and the levels/types of fat in diets ... with any scientific funding investigating the impact of sugar on obesity increasingly switched off!
The food industry (particularly the sugar/corn companies) did this as, following their creation/manufacture of High Fructose Corn Syrup (nb basically a very cheap type of sugar, containing a glucose/fructose mix), they saw a great opportunity in the marketing of "low fat" products packed full of ultra cheap (and sweet) High Fructose Corn Syrup (HFCS) ... and selling it for a premium!
... and consuming large volumes of fructose turns out to be a huge problem ... for two fundamental reasons:
1. Fructose is 'processed' by the body in a completely differently way to other carbohydrates ... unlike glucose, fructose cannot be metabolised directly by cells and it all has to be broken down by the liver (nb where poisons are processed). The process of transformation in the liver involves fructose being turned into uric acid, but also into dangerous fats which enter the bloodstream and get deposited around the body (nb additional chemicals created from breaking down fructose also enhance/accelerate this whole process further)! So 'low fat' (and highly processed) foods containing fructose are actually a way of pumping the body full of fat ... i.e. people are being duped into a terrible form of 'high fat' diet (i.e. that creates high levels of body fat) ... and are not on a 'low fat' diet at all ... and as all the advertising around it might suggest!
2. This first problem is further exacerbated by yet another fundamental problem with fructose ... the fact that the consumption of fructose does not surpress ghrelin (i.e. the hunger hormone generated by the stomach) and it doesn't stimulate insulin or leptin (i.e. the hormone that tells the brain that your body is already metabolising food, in order to surpress further intake) ... so people still feel hungry and continue to eat!
Fructose delivered to the food industry the perfect solution ... a way of making people feel continually hungry so they'll consume more ... and all under the 'banner' of healthy 'low fat' foods! 'Low fat' foods are mostly full of cheap sweet fructose, as it's used to replace all the taste lost from removing the fat (nb food tastes like cardboard without it)! You couldn't make this stuff up ... and yet it's all true (e.g. take a look at the video below from a world leading endocrinologist who attempts to explains it all ... including the biochemistry)!