On the flip side....
The GI of foods is determined by asking the subject to completely fast for 8 hours, then eat the specific single food or ingredient, then they do a blood test. Therefore, the GI of a food is only valid if you eat just that single food on an empty stomach. If you combine two foods in the same meal, it's impossible to know the GI of your meal. Also if you chop your vegetables smaller, chew them more or fewer times, cook them 30 seconds longer, add butter or any other ingredient, then the GI changes. Pasta made in Canada and cooked for precisely 8 minutes had a different GI than pasta made in America also cooked for the same 8 minutes. There are so many variables in place that many dietitians ignore it.
In 2005, the results of a major study were released that seemed to dispute the validity of the GI. The study was funded by the National Institutes of Health and was conducted at a university. They followed over 1,000 people over 5 years and found no connection between high GI foods and elevated blood sugar.
In another study, subjects followed either low or high GI diets for 12 weeks. Both groups were on reduced calorie diets. Both groups lost the same amount of weight. Both groups showed the same amount of improved insulin function, and it was concluded that the weight loss itself was responsible for the improvement, rather than the specific foods eaten.
On the other hand, foods that are lower GI are generally very healthy foods, with decent amounts of fiber and other nutrients. You can't go wrong by choosing them. Focusing on something like the GI encourages you to make more careful food selections, leaving out a lot of junk and empty calories.
BUT, and there's always a but
If you have been tested and diagnosed insulin resistant, then you could benefit from a low GI or low GL (glycemic load) diet. For everyone else, the evidence shows no effect.
What's "Glycemic Index" all about???
