"In my video Are Green Smoothies Bad for You?, I show you the rise and fall of blood sugar and insulin over four hours after eating a half-cup of brown rice compared with ground brown rice flour (kind of like a cream of brown rice hot cereal). Consuming brown rice flour gives you twice the blood sugar and twice the insulin spike compared to eating the rice intact. Same amount of food, just in a different form. This is why intact whole grains are better than even whole grain flour products."

… 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.”

Another way to feed our good bacteria is to eat intact grains, beans, nuts, and seeds.

In one study, researchers split people into two groups and had them eat the same food, but in one group, the seeds, grains, beans, and chickpeas were eaten more or less in a whole form, while they were ground up for the other group. For example, for breakfast, the whole-grain group got muesli, and the ground-grain group had the same muesli, but it was blended into a porridge. Similarly, beans were added to salads for the whole-grain group, whereas they were blended into hummus for the ground-grain group.

Note that both groups were eating whole grains—not refined—that is, they were eating whole foods. In the ground-grain group, though, those whole grains, beans, and seeds were made into flour or blended up.

What happened? Those on the intact whole-grain diet “resulted in a doubling of the amount excreted compared to the usual diet and produced an additional and statistically significant increase in stool mass” compared with those on the ground whole-grain diet, even though they were eating the same food and the same amount of food. Why?

On the whole-grain diet, there was so much more for our good bacteria to eat that they grew so well and appeared to bulk up the stool. Even though people chewed their food, “[l]arge amounts of apparently whole seeds were recovered from stools,” but on closer inspection, they weren’t whole at all. Our bacteria were having a smorgasbord. The little bits and pieces left after chewing transport all this wonderful starch straight down to our good bacteria. As a result, stool pH dropped as our bacteria were able to churn out so many of those short-chain fatty acids. Whole grains are great, but intact whole grains may be even better, allowing us to feed our good gut bacteria with the leftovers.

"Instant oats are better than powdered oats, rolled oats are better than instant, steel-cut oats are better than rolled, and intact oat groats are the best of all!"

"As I discuss in my video Which Is a Better Breakfast: Cereal or Oatmeal?, the physical form of food alters carbohydrate absorption. Rolled oats, for example, 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. Indeed, the same single ingredient–oats, in this case–can have different effects in its different forms."

"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. Researchers fed a dozen obese teen boys different meals, each with the same number of calories, and followed them for the next five hours to measure their subsequent food intake. Those who ate the instant oatmeal went on to eat 53 percent more than the boys who ate the same number of calories of steel-cut oatmeal. The instant oatmeal group was snacking within an hour after the meal and went on to consume significantly more calories throughout the rest of the day. Same food but different forms had different effects."

"It’s crazy how the same product can have such different effects on the body, based on how it’s processed. Beyond focusing just on whole rather than refined grains, the wholiest of all are intact grains."

Rolling crushes the grain, which may disrupt cell walls and damage starch granules, making them more available for digestion — which is bad, since we want the starch to make it all the way down to our colon to feed our good gut bacteria. Grinding into oat flour to make breakfast cereals is even worse. If you compare the blood sugar and insulin responses, you can see significantly lower spikes with the more intact steel-cut oats.

"I am often asked if there is any harm in using a home-bread-machine to make bread — after all, nothing is added or removed in the processing. For most people whole grain breads are an excellent choice, but it is not the same as eating whole grains. Beating the whole grain more than 1000 times with the whirling steel blade of the bread machine converts the kernel into a powder, known as flour. The intact cell wall of the kernel has been destroyed and now the digestive enzymes (amylase) easily digest the inner nutrients. In addition, the flour has a much larger surface area to volume ratio than did the whole grain, making digestion and absorption much more rapid. For you this physical change may translate into easier weight gain, and higher blood levels of glucose, triglycerides, and cholesterol. The amount of insulin released by the pancreas into the blood is also increased as grains are processed from whole grains to cracked grains to coarse flour to fine flour.[23] More insulin can mean more weight gain, and maybe, more risk of diabetes and heart disease. However, compared to animal-foods, free-oils, and plant-parts processed beyond recognition, whole wheat bread is definitely health food."

At the very bottom of the Whole Grain Hierarchy are what we call 'puffed grains'. So we are talking about things like puffed rice, puffed wheat crispies, even the Cheerio-type cereals, or even something that people believe is one of the healthiestfoods that they can eat: brown rice cakes. Now this is made from brown rice. It's a whole grain food. But if you look at the rate of absorption and the destruction of nutrients that results from the puffing process, it's actually quite shocking! Puffed rice cake might have a glycemic index of 100 in comparison to sugar which has a glycemic index of 68. Its rate of absorption is very very high and quick. So these foods (puffed grains) are the least desirable.