According to the website www.glycemicindex.com,
"Not all carbohydrate foods are created equal, in fact they behave quite differently in our bodies. The glycemic index or GI describes this difference by ranking carbohydrates according to their effect on our blood glucose levels. Choosing low GI carbs - the ones that produce only small fluctuations in our blood glucose and insulin levels - is the secret to long-term health reducing your risk of heart disease and diabetes and is the key to sustainable weight loss."
Yeah right!! Glycemic Index is a system that estimates amount our blood sugar will rise after consuming 50 grams of the carbohydrate in question. that estimates the amount of blood sugar rise one will encounter after consuming 50 grams of a particular form of carbohydrate. For example, eating 50 grams of carbs from potato is said to cause a larger blood glucose spike than eating 50 grams of carbohydrate from a Mars Bar (A US Mars Bar is higher than an Australian version).

So the potato has a slightly higher index rating with the skin and a huge rating (big cheer for the formally humble potato), if you dare eat it without the skin. Lot easier and quicker to get those carbs from a Mars Bar though isn't it?
To counter this scientists brought along glycemic load (GL) to the party. So, we now have to think about GI and GL, confused yet? This attempts to try and even things out a little but in their own words "a diet with a low GL, unfortunately, can be a ‘mixed bag’, full of healthy low GI carbs in some cases, but low in carbs and full of the wrong sorts of fats such as meat and butter in others. If you choose healthy low GI foods—at least one at each meal—chances are you’ve eating a diet that not only keeps blood glucose ‘on an even keel’few grams of carbs, and has an insignificant impact on blood sugar – unlike a Snickers bar by volume." So, appropriately, the Mars Bar (27) registers higher on a calculation for glycemic load than potato (19 with skin, 26 without skin), and they tell you to stick with the GI recommendation that insists the Mars Bar is the better option.
Damn confusing for the public and not a great option for gaining optimum health which I'll cover in a future post.