There are literally dozens of types of sugar which are all different and have different effects in the body. "Sugar is sugar" is completely false.
The Corn Refiners Association popular commerical "Sugar is Sugar" tries to claim that high fructose corn syrup (HFCS) is just like cane sugar (regular table sugar).
http://www.youtube.com/watch?v=Fyj2N-AspqU
A Princeton University study showed again what everybody knew from experience, that high fructose corn syrup (HFCS) - which is the main ingredient in most sodas and lots of junk food - is more fattening than regular table sugar.
http://www.princeton.edu/main/news/archive/S26/91/22K07/
A 2009 study featured in Time magazine had a similar finding:
All Sugars Aren't the Same: Glucose Is Better, Study Says
http://www.time.com/time/health/article/0,8599,1892841,00.html
On top of this, the commercial presents HFCS as "corn sugar", a seemingly natural product, which it is not by a longshot. Dextrose (a form of glucose), not HFCS, is the natural sugar found in corn and it is not a health problem, in fact it is what bodybuilders take post-workout because it is sugar in simplest form. HFCS, on the other hand, is an artificial substance created by putting corn starch through a series of three industrial enzymatic processes.
HFCS has also been implicated as the primary source of AGEs (Advaced Glycation End Products) which are now known to cause cardiovascular problems (esp. endothelial dysfunction) as well as Alzheimer's.
Moreover, even a basic understanding of sugars and how humans process them tells you that "sugar is sugar" is false. There are many types of sugars which are processed very differently by the body. Some are processed in the liver, some in the intestines, some do not need processing at all. Moreover, different sugars require different enzymes to break them down, ex. starches require amylase enzymes, sucrose needs sucrase, etc. and different people have more or less of these enzymes which results in differing abilities among people to break down different types of sugars.
For example, all of these are chemically different categories of sugars:
Monosaccharides - glucose/dextrose, fructose, galactose, xylose and ribose
Disaccharides - sucrose and lactose
Polysaccharides - starches (from bread to potatoes to rice etc.) and glycogen (stored sugar in muscle and liver)
