Save hundreds of calories by chosing the right food structure
Tuesday, February 09, 2021
"The physical form of food can not only alter fat absorption but carbohydrate absorption as well. It comes as no surprise that Rice Krispies and Corn Flakes cause a much greater spike in blood sugars than rice or corn on the cob, but it's not just the added sugar in the cereals. Even with identical ingredients, food structure can make a big difference. For example, rolled oats have a significantly lower glycemic index than unsweetened instant oatmeal, which is also straight oats but in thinner flakes, and oat FLAKES cause lower blood sugar and insulin spikes than POWDERED oats. The same single ingredient, oats, in different forms can have different effects.
Why do we care? As i noted in the Low Glycemic Load section, the overly rapid absorption of carbohydrates after eating a high-glycemic index meal can trigger a sequence of hormonal and metabolic changes that promote excessive eating.
In a study out of Harvard's Childrens' Hospital, a dozen obese teen boys were fed instant oatmeal versus steel-cut oatmeal. After the instant oatmeal, the teens went on to eat 53 percent more than after eating the exact same number of calories of steel-cut oatmeal. The instant-oatmeal group was snacking within an hour after the meal and went on to acccumumlate significantly more calories througout the rest of the day. Same type of food, but different form, yielding different effects.
Steel-cut oatmeal is considered a low-glycemic-index food, averaging under 55. The glycemic index of instant oatmeal is 79, making it a high-glycemic-index food, but not as bad as some breakfast cereals, which can get into the 80's or 90's. This is even true of zero-sugar cereals like shredded wheat. The new industrial methods used to create breakfast cereals, such as extrusion cooking and explosion puffing, accelerate starch digestion and absorption, causing an exaggerated blood sugar response. Shredded wheat has the same ingredients as spaghetti - straight wheat - but twice the glycemic index.
When you eat spaghetti, you get a gentle rise in blood sugars. If you eat the same amount of wheat baked into bread form, hoever, you get a big spike in blood sugars. All the little bubbles in bread allow our bodies to break it down so fast that it can cause our bodies to overreact with an insulan spike so large it can drive down our blood sugars below fasting levels. This hypoglycemic dip two hours after breaking bread can then trigger hunger sensations. Experimentally, if you infuse someone with insulin so their blood sugars fall, you can cause their hunger to rise, and, in particular, spike cravings for high-calorie foods. In short, lower-glycemic-index foods may help us feel fuller longer than the equivalent higher-glycemic-index foods.
A dramatic illustration of this effect was demonstrated by researchers at Columbia Unversity. Individuals were randomized into one of three breakfast conditions - oatmeal made from quick oats, the same number of calories of Frosted Flakes, or just plain water - and then the researchers measured how much the subjects ate for lunch three hours later. Unsurprisingly, those who had eaten the oatmeal felt significantly fuller and less hungry after a few hours and indeed went on to eat significantly less lunch. Overweight participants in the oatmeal group ate less than half as many calories at lunch, hundreds of fewer calories compared to the other groups. How did the cereal group fare? The breakfast cereal was so unsatiating that the Frosted Flakes group ate as much lunch as the breakfast-skipping water-only group. It's as if the cereal group hadn't eaten any breakfast at all."
From: "How not to Diet" by Michael Greger, p. 546-547