It’s not all about the calories nor about all carbohydrates but a specific one. This diagram shows the comparison of the major pathways for the fate of either A) 100 g of glucose (from starch) or B) 100 of sugar (50% glucose and 50% fructose). A). After digestion of starch 1), glucose enters the portal vein 2). In the liver it is converted, in part, to glycogen 3) and most of it goes into the bloodstream 4) to feed the tissues as it increases insulin secretion 5) and glucose enters muscle and adipose tissues 6). The rest is used to fuel the liver itself via glycolysis 7) leading to Acetyl coenzyme A (AcCoA) 8) which generates energy in the mitochondria. Very little is converted to fat 9) via the process of de novo lipogenesis (DNL). B). After digestion of sugar 1), glucose and fructose enter the portal vein in equal amounts 2). In the liver, glucose will be turned, in part, into glycogen 3). Most of it enters the bloodstream 4) to feed the tissues as it increases insulin secretion 5) and glucose enters muscle and adipose tissues 6). Fructose does not leave the liver for the most part. Instead, it is quickly phosphorylated by FFK C, bypassing regulatory steps in glycolysis and flooding the system 7), 8). The trapped metabolites have one fate: they are turned into fat by de novo lipogenesis 9) and 10). This process impairs FA oxidation by the mitochondrion because malonylCoA inhibits carnitine palmitoyl transferase I (CPT I) and FA transport into the mitochondrion 9). Some of the trioses are also transformed into the toxic metabolite methylglyoxal (MG), which can be detoxified to D-lactate 11). These processes have dire consequences as explained in the next figures. Finally, as further developed in other diagrams, quick phosphorylation of fructose leads to energy depletion and uric acid production, which in turn stimulates fructose metabolism 12).