Fructose just has to be the best bit, it is what everyone (except me) is after, and it is the taste they chase. Common sugar sucrose is one molecule of fructose bound to another molecule of glucose, whilst the body is fuelled by glucose, it is boring stuff and doesn’t taste sweet all!
Our primal hunter gatherer ancestors evolved to make the best use of fructose, it is thought their diet was mainly animal fat and protein and plant material, recent examination of fossil teeth residues implies that the plant materials were actually partially digested prey animal stomach contents. Inevitably, their diet, being low in carbohydrate, would have been ketogenic, they would have gained energy from endogenous (liver produced) glucose from gluconeogenesis of animal fat and protein. The problem here is, it is very difficult to lay down fat on such a diet.
Fructose on the other hand cannot directly be processed into energy in the human body; the liver has to convert fructose into fat! Ideal for our primal ancestors, during summer and autumn, berries and wild fruits would have abounded. Enticed by the, relative, sweetness our ancestors would have had a field day scoffing this bounty, nicely fattening themselves up in preparation for a long and meagre winter.
Our inability to convert fructose directly into energy conferred an evolutionary survival advantage.
Having survived this far, and having modern advantages for survival, such as central heating and an inexhaustible food supply, we should leave the sweet stuff alone. The survival advantage has turned into a threat to our survival.
Refined sugar is completely unnatural and in our modern world should be completely avoided at all costs. Imagine how much yardage of sugar cane you would have to chew, to get the equivalent of a Mars bar!
If it tastes sweet, its purpose is to fatten you up, that of course includes fruit. The problems with endogenous fat are; 1, it makes your liver fatty. 2, it makes you fatty, 3, The Very Low Density Lipid particles that the liver produces from fructose raise triglycerides and risk of Coronary Heart Disease, and finally end up as LDL cholesterol.
Fattening up for winter is good (if you are a caveman) - Fattening up for a lifetime is bad, very bad!