Boiled potatoes & Area Under the Curve (AUC): some thoughts.

Here are three "curves"... a 4 x 1 rectangle, a 2 x 2 square and a 1 x 4 rectangle.

The AUC for all three "curves" = 4.

Imagine that the three curves are for blood glucose level increase above baseline vs time.

a) "X" grams of a high-Glycaemic Index (GI) carb e.g. glucose, maltodextrin or amylopectin will result in a large glucose response that goes away rapidly, as the carbs pass into the blood rapidly and are cleared from the blood rapidly due to the large insulin response.

b) "X" grams of a 50:50 mixture of high & low-GI carbs will result in a lower but longer sustained glucose & insulin response, as the carbs (are converted into glucose slowly and) pass into the blood slowly and are cleared from the blood slowly due to the small insulin response.

c) "X" grams of a low-GI carb e.g. amylose or resistant starch will result in an even lower glucose & insulin response that is sustained for even longer, as the carbs (are converted into glucose very slowly and) pass into the blood very slowly and are cleared from the blood very slowly due to the very small insulin response.

Will a), b) & c) produce the same satiety? I think not. I think that a) will produce lower satiety than b) or c). Whether hunger is caused by a sudden drop in blood glucose level or by a sudden drop in the amount of nutrients in the gut, I don't know.

The reason for this post is A satiety index of common foods (full study) and the related study An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods.

In the first study, boiled potatoes produced the highest satiety, yet in the second study, boiled potatoes produced one of the highest glucose & insulin AUCs. How can this be? Consider the preparation method for the Russet potatoes:-
"Peeled, boiled for 20 min, and stored at 4 °C overnight; reheated in a microwave oven for 2 min immediately before serving."

Potato starch when refrigerated, produces resistant starch, which has a low GI (see item 605 in International table of glycemic index and glycemic load values: 2002). Therefore, refrigerated potatoes contain a mixture of high & low-GI starches. This, I believe, is why boiled, refrigerated & reheated potatoes produced the highest satiety. The combination of water, fibre & resistant starch kept hunger pangs away the longest. I suspect that boiled potatoes that are eaten hot won't produce as much satiety, as they contain no resistant starch.

Has anyone compared the satiety of freshly-boiled potatoes with boiled & refrigerated potatoes?