Not all types of sugars are bad.  Here are different types of sugars and the affects they have on your system: Glucose: Glucose is a simple sugar that your body likes.  All of your cells use Glucose as their primary source of energy.  Glucose is necessary for your body to function.  After Glucose is ingested,  it sends signals to the pancreas to produce insulin. Signals are then sent to the brain and metabolizes the food just eaten.  When the brain notices the food intake, it lets the rest of your body know that you are not hungry.  So, glucose basically lets your brain know that you are finished eating and that you don't need to eat anymore. Glucose, though natural, can have some issues for the body as well.  Your liver will produce what are called very low density lipoprotein (VLDL).  This is considered a bad cholesterol.  VLDL can cause cardiovascular disease.  Only 1 out of 24 calories ingested and processed by the liver turn into VLDL. Sucrose and High Fructose Corn Syrup: These two are linked together here because high fructose corn syrup (HFCS) and sucrose are really the same thing.  They are both contain a large amount of fructose and are highly sweet.   Sucrose is 50% fructose and HFCS is 55% fructose. The other remaining percentages consist of glucose. In most cases, fructose is bad for you because of how the body processes it. Fructose can only be metabolized by the liver, which means a greater number of calories (about three times more than glucose) are metabolized by the liver and higher amounts of VLDL.  It also creates a larger amount of uric acid which leads to hypertension and high blood pressure. Fructose also has negative affects on the brain regarding what you have consumed.  This happens because it alters a protein called "Leptin."  This protein is important for energy intake and expenditure and is key for monitoring your appetite and keeping your metabolism working the way it should.  When you eat fructose, your body resists Leptin and you feel hungry even when you are not.  So, foods like soda contain high amounts of fructose which then trick your brain into thinking you are not full and your body thinks you are still hungry.  There have been studies showing that people who have consumed Fructose actually eat more than people who do not. Processed v. Unprocessed Foods: Fruit contains fructose, but as shown on the food pyramid, it shows that fruit is okay. How is that possible?  Well, it is because fruit is all natural and has large amounts of fiber.  Fiber monitors your satiety levels even though fructose does not.   This is why fruit is beneficial. The same goes for processed sugar. Sugar doesn't exist naturally as the sugar that you buy at the store, but as a really tough stick called sugar cane.  It isn't until you process the sugar can that all the fiber is taken out of it.  Without the fiber, you only have the bad portion of the sugar.  That's why processed sugars can cause problems.