Each part of the list has specific reasons to leave these out of the diet. Sugar in the simplest is empty calories, without any nutritional value, but that is not all. Sugar is one glucose bonded to one fructose molecule. It is split by an enzyme found in the saliva, and absorbed in the mouth, esophagus, stomach, and upper intestine, at a rate up to 20 grams per minute. It does not hang around, when it is free, it just gets absorbed.
Fructose goes to the liver, little gets past. Blood concentration in namograms per litre, namomoles per litre,( atomic weight 180). It is converted into glycogen, up to perhaps 100C worth, and then into saturated fats. It causes insulin to lock in the fat, and some insulin to be generated, some think.
The glucose goes to the liver after absorption, and passes through, the pancreases releases insulin, and the fat cells soak up the blood glucose like mad. The blood only carries perhaps 1 gram, so it is being soaked up almost as fast as it goes in. In the fat cell, it is converted to saturated fat for storage.
Now we have to go through the hunger stage, get insulin low, burn the livers stores of glycogen, before we can get to that fat to burn it. Sugar, in any quantity is not a good diet food. Having said that, a couple of grams per hour may help stabilize blood sugar, in some cases. (see R Bernstein, 2 gram solution in the Diabetes Solution).
Sugar and its more evil twin, HFCS, high fructose corn syrup, what ever it is called, along with those other names for the glucose fructose stuff, is essentially wonderful tasting poison once it is separated from fibre. Fibre slows digestion a bit.
The poison is in the dose. Do not eat poison if you can avoid it. and for the who missed them, here is a list of videos http://philosophyofweightmanagement.blogspot.ca/p/links.html