Glycemic Index Fails to Help You

A Word about the Glycemic Index and Why It Does Not Work!

The glycemic index is a popular way to numerically grade carbohydrate foods based upon the criteria of how much and how quickly the food results in elevated glucose in the bloodstream. This laboratory-derived list of foods is found in every reference work on diet and nutrition. The glycemic index is inappropriately but commonly used as evidence that a particular food is “good” or “bad.” The logic of the glycemic index follows that good carbs are slow to result in glucose in the bloodstream, while bad carbs are faster to result in measurable blood glucose. Of course, foods that have no carbohydrate content are not on this scale, so fats and proteins have no inherent glycemic response.

There are problems with the overly simplistic glycemic index. Here are three reasons why you will not find the ubiquitous “glycemic index” in The Blood Code:

Reason #1: Food combination, like in a “balanced meal,” is not accounted for in the glycemic index. Fat and soluble fiber with the meal effectively lowers the glycemic index of any carbohydrate food at that meal. The same effect is also seen if fermented foods and vinegar are added to a carbohydrate meal.

Reason #2: Excess glucose from carbs can clearly aggravate insulin resistance, but too much pure protein and large-volume meals trigger a problematic release of insulin, despite their lack of effect on blood sugar.[i]

Reason #3: I have saved the biggest reason for last: Fructose! Fructose is very low on the glycemic index, so it actually ends up in the “good” category, but fructose delays its harmful effect. Your body cannot immediately access the glucose molecule bound up in the fructose molecule. Many hours after you eat, fructose—whether from fruit or a processed sugar—gets converted into glucose, glycogen, lactate, and fat in the liver. There is a strong and adverse impact on the liver itself; fatty liver and insulin resistance are made worse through the ingestion of fructose. It is swiftly turned into fatty liver, and can strongly trigger insulin resistance. The glycemic index of foods wrongly rewards high-fructose foods, because the index is only attentive to immediate glucose in the bloodstream; the delayed and harmful effect of fructose is neglected.[ii]

I do realize that others recognize the failure of the Glycemic Index, and this awareness has given rise to another way to list carbohydrate foods using an Insulin (response) Index.  This Insulin Index is even more flawed – for the same reasons listed above and the fact that there is a 6-8 fold difference in insulin output given the same intravenous glucose load from one person to another in the non-diabetic population. This is such a HUGE discrepancy that no valid information can be drawn from such an index for the “average” person. You therefore must know your own Insulin and insulin resistance profile – as you would find in your Progress Panel.


[i] Holt, S., et al. An insulin index of foods: The insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr 1997; 66:1264–76.

[ii] Tappy, L., et al. Metabolic effects of fructose and the worldwide increase in obesity. Physiol Rev. 2010 Jan; 90:23–46.