The GI concept, some interesting news.

[Rahf]

Diabetes Care 28:2832-2838, 2005, Dietary Glycemic Index and Glycemic Load, Carbohydrate and Fiber Intake, and Measures of Insulin Sensitivity, Secretion, and Adiposity in the Insulin Resistance Atherosclerosis Study

"We studied the association of digestible carbohydrates, fiber intake, glycemic index, and glycemic load with insulin sensitivity (SI), fasting insulin, acute insulin response (AIR), disposition index, BMI, and waist circumference.

Data on 979 adults with normal (67%) and impaired (33%) glucose tolerance... were analyzed.

No association was observed between glycemic index and SI, fasting insulin, AIR, disposition index, BMI, or waist circumference after adjustment for demographic characteristics or family history of diabetes, energy expenditure, and smoking.

Associations observed for digestible carbohydrates and glycemic load, respectively, with SI, insulin secretion, and adiposity (adjusted for demographics and main confounders) were entirely explained by energy intake.

Carbohydrates as reflected in glycemic index and glycemic load may not be related to measures of insulin sensitivity, insulin secretion, and adiposity."

J Nutr. 2005 Oct;135(10):2387-91. Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women.

"Reducing the dietary glycemic load and the glycemic index was proposed as a novel approach to weight reduction. A parallel-design, randomized 12-wk controlled feeding trial with a 24-wk follow-up phase was conducted to test the hypothesis that a hypocaloric diet designed to reduce the glycemic load and the glycemic index would result in greater sustained weight loss than other hypocaloric diets.

At 12 wk, weight changes from baseline were significant in all groups but not different among groups (-9.3 +/- 1.3 kg for the HGI diet, -9.9 +/- 1.4 kg for the LGI diet, and -8.4 +/- 1.5 kg for the HF diet). All groups improved in insulin sensitivity at the end of the feeding phase of the study. During the free-living phase, all groups maintained their initial weight loss and their improved insulin sensitivity.

Weight loss and improved insulin sensitivity scores were independent of diet composition.

In summary, lowering the glycemic load and glycemic index of weight reduction diets does not provide any added benefit to energy restriction in promoting weight loss in obese subjects."

Diabetes Care. 2005 Sep;28(9):2123-9. Influence of glycemic index/load on glycemic response, appetite, and food intake in healthy humans.

High glycemic index (GI)/load (GL) diets reportedly enhance appetite and promote positive energy balance. Support for this hypothesis stems largely from acute feeding trials and longer-term studies lacking control over the macronutrient composition and palatability of test foods. This study evaluated the effects of consuming high- and low-GI/GL meals, matched on macronutrient composition and palatability, plasma glucose and insulin, appetite, and food intake.

Thirty-nine healthy adults consumed only low- or only high-GI foods ad libitum in the laboratory for 8 days in either high (three foods per meal)- or low (one food per meal)-variety conditions. Glucose and insulin concentrations as well as appetitive sensations were determined before and for 2 h following breakfast and lunch on days 1 and 8. Energy intake was monitored daily.

There were no significant differences in plasma glucose or insulin responses, appetitive ratings, or food intake between treatments.

These data indicate that the differential glycemic response of foods tested in isolation under fixed time are not preserved under conditions of chronic ad libitum consumption of mixed meals."

In short: GI has no effect on weightloss, insuline sensitivity, overweight, insuline response, insuline levels, hunger or food intake. It's the energy intake that is the deciding factor.

It's impossible to use the GI numbers given in isolated studies or given in GI-listings. That is on a normal diet.

The numbers are in this case obsolete! Eat unprocessed, unrefined, nutrition rich and natural = GI is irrelevant.

I hope this comes as a happy message to some of you who think you could never eat white bread again. Perhaps sticky so people won't have to wonder about GI ever again?

[Ashtar]

Even if insulin insensitivity is due more to long-term carbohydrate load than whether or not it spikes, spikes are still more dangerous to those who are insensitive as it raises the blood sugar more at once.

Another thing is if you ARE sensitive, a spike still sucks because unless your glycogen is well depleted (as in, post-exercise excepted), there can easily be some excess beyond what your muscle and liver can store, and it gets stored as fat.

Which isn't horrible and it's good to do that a little to guarantee your energy stores are peaked, but too much, may as well have some fat, less metabolic work involved.

[Rahf]

Even if insulin insensitivity is due more to long-term carbohydrate load than whether or not it spikes, spikes are still more dangerous to those who are insensitive as it raises the blood sugar more at once.

Another thing is if you ARE sensitive, a spike still sucks because unless your glycogen is well depleted (as in, post-exercise excepted), there can easily be some excess beyond what your muscle and liver can store, and it gets stored as fat.

Which isn't horrible and it's good to do that a little to guarantee your energy stores are peaked, but too much, may as well have some fat, less metabolic work involved.

As stated, if you have normal eating habits you'll be fine. Your comment is void in regard to the study.

[NightHunter]

These are some interesting studies. There is still an argument to be made for micronutrient content, but that's obviously a different issue than these tackled.

[SolidD33]

The only time the GI of a food comes into play is if it's eaten by itself. So it all depends on the different food combinations people use within their nutrition program.

If I eat two chicken breasts and then three slices of white bread, my GI load for that meal is radically lower than eating that white hazardous waste by itself.

The GI really doesn't help too much in accounting for a meals level of GI load or following insulin secretion, since most people eat foods in combination with other foods.

Nonetheless, eating white bread isn't something those concerned with long term health and body composition should be doing.

[Ashtar]

The comment isn't entirely void to the study, it is easier to 'overfeed' with spikes that will convert carbohydrates to fat storage, fats that will only burn aerobically. Sugars can be burned anaerobically in a much less efficient manner, leading to greater energy expenditure. Spikes are better for gaining weight.

How much it spikes is often a good evaluation for density as well. Things that don't spike usually have a lot of fibre in them which mitigates the release, and that always adds bulk to reduce the caloric density of the food. Plus the fibre's just generally good intestinal stimulation and good for avoiding excessive cholesterol if it's an issue.