A lot of it has to do with the "glycemic index", which is a measure of how quickly a particular nutrient enters the bloodstream and how much demand for insulin it places upon your endocrine system.
The top of the heap is regular sugar, sucrose, with a glycemic index of 100, against which everything else is measured. It gets to your blood the fastest, demands the greatest amount of insulin, and gets converted to fat the quickest, if your body does not need to burn it for energy right then.
Hence the reason that most of us are so fat!
You are well advised to read all those labels very carefully. Even the Atkins Bars have way too much carb, IMO. This WOE is much easier, and much more effective, for those who cook their own high protein/high fat foods for themselves and stay away from the hidden carbs that are laced in nearly all "convenience" food. IMHO, of course!
A really good idea is to get your own pocket size carb counter, and to read two or three of the low carb books, if you have not done that yet. I find that Dr. Atkin's "New Diet Revolution" and Drs. Eades "Protein Power", have been the most useful for me.
YMMV
Good luck, and keep on, keepn' on!