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“Food structure,” not just nutrient composition, may be “critical for optimal health.” It should come as no surprise that cornflakes and Rice Krispies cause a much greater spike in blood sugars than rice or corn-on-the-cob; but it’s not just the added sugar. “Even with identical [ingredients], food structure can make a major difference…” For example, if you compare the absorption of fat from peanuts, compared to the exact same number of peanuts ground into peanut butter, you flush more than twice the amount of fat down the toilet when you eat the peanuts themselves, since no matter how well you chew, small bits of peanuts trap some of that oil makes it down to your colon. And, “the physical form of food” not only alters fat absorption, but carbohydrate absorption as well. For example, rolled oats have a significantly lower glycemic index than instant oatmeal, which is just oats, but in thinner flakes. And, oat flakes cause lower blood sugar and insulin spikes than powdered oats. Same single ingredient: oats, but in different forms can have different effects.

Why do we care? Well, the overly “rapid absorption” of carbohydrates after eating a high-glycemic index meal can trigger “a sequence of hormonal and metabolic changes” that may promote excessive eating. They took a dozen obese teen boys and fed them different meals, each with the same number of calories, and just followed them for the next five hours to measure their subsequent food intake. And, those that got the instant oatmeal went on to eat 53 percent more than after eating the same number of calories of steel-cut oatmeal. The instant oatmeal group was snacking within an hour after the meal, and goes on to accumulate significantly more calories throughout the rest of the day. Same food, but different form; different effects.

Instant oatmeal isn’t as bad as some breakfast cereals, though, which can get up into the 80s or 90s—even a cereal with zero sugar like shredded wheat. The “new [industrial] methods” used to create breakfast cereals, such as extrusion cooking and explosive puffing, accelerate starch digestion and absorption, causing an exaggerated blood sugar response, added sugar or not. Shredded wheat has the same ingredients as spaghetti—just wheat—but has twice the glycemic index.

When you eat spaghetti, you get a gentle rise in blood sugars. If you eat the exact same ingredients made into bread form, though, all the little bubbles in bread allow your body to break it down quicker; so, you get a big spike in blood sugars, which causes our body to overreact with an exaggerated insulin spike. And, that actually ends up driving our blood sugars below fasting levels, and that can trigger hunger. Experimentally, if you infuse someone with insulin so their blood sugars dip, you can cause their hunger to spike, and, in particular, hunger cravings for high-calorie foods. In short, lower-glycemic index foods may “help one to feel fuller longer than equivalent [higher-glycemic index] foods.”

Researchers randomized individuals 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 measured how much people ate for lunch three hours later. Not only did those who ate the oatmeal feel significantly fuller and less hungry…they indeed then went on to eat significantly less lunch. Overweight participants ate less than half as many calories at lunch after eating the oatmeal for breakfast—hundreds and hundreds of calories less. In fact, if you notice, the breakfast cereal was so unsatiating that the Corn Flakes group ate as much as the breakfast-skipping, water-only group. It’s as if the cereal group hadn’t eaten breakfast at all!

Feed people Honey Nut Cheerios, and hours later they feel significantly less full, less satisfied, and more hungry than those fed the same number of calories of oatmeal. Though both breakfasts were oat-based, the higher glycemic index, reduced intact starch, and reduced intact fiber in the Cheerios seemed to have all conspired to diminish appetite control. “The trial was funded by the Pepsi Corporation,” makers of the Quaker oatmeal, pitted against the Cheerios from rival General Mills. And an exposé on industry-funded study manipulation later revealed that the study originally included another arm, Quaker Oatmeal Squares. “I am sorry that the oat squares did not perform as well as hoped,” the researcher told Pepsi, which “decided to publish only the results about its oatmeal.”

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