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Before we jump into a very fascinating topic, I must first mention that my latest bestselling book (#1 of 22,000 listings in Nutrition on Amazon), Eat for Heat: The Metabolic Approach to Food and Drink, is currently available at a heavily-discounted price.  If you haven’t had the chance to read it yet, now’s the time to get it – and tell your friends about it too.  Buying it, pressing the “like” button, and writing a short 1-paragraph review while you’re there would be a big help in moving it ahead of all the constipation-inducing, sex-drive killing, and otherwise metabolically-suppressive diet books currently ranked above it.  If you’ve already purchased it, consider giving a 99-cent “donation” by scooping it up on Amazon, or buying it for a friend or family member perhaps.  Any help you can stir up would be great, as more eBooks are bought the week after Christmas than at any other time, and there are lots of icy cold people out there that really need to read it.  Without your help it will stay buried in obscurity, and ill people will be downloading Wheat Belly or something by Joel Fuhrman instead. Click the following link to participate in Operation Friends Don’t Let Chilly Strangers Go On Low-Carb Gluten-Free Low-Calorie Vegetarian Diets (OFDLCSGOLCGFLCVD) Eat for Heat

Okay, back to bowels…

It’s well-known, although not necessarily widely talked about in mainstream media, that gut bacteria exerts a great deal of influence over body weight – or at the very least obesity-proneness.  A “landmark” study was released just a couple of weeks ago discussing the role of intestinal bacteria in controlling obesity and one man’s elimination of a certain bacterial strain that resulted in relatively effortless weight loss of over 100 pounds.  There are multiple schools of thought on this.  In this post we can talk about a couple of prevalent theories and see how that relates to real-world, real-life personal experience on behalf of those reading this.

Most believe that the type of bacteria inhabiting the gut, not necessarily bacteria themselves, have a big influence over body weight.  Gut bacteria have been subdivided into two classes – firmicutes (shown left) and bacteroidetes.  Linda Bacon discusses this in her excellent book Health at Every Size

“Fatter people tend to have a significantly greater proportion of one of the two main types of bacteria found in the gut, known as Firmicutes, than the other, known as Bacteroidetes.  Detailed molecular analyses show that the Firmicutes are much better at extracting calories from food.

When researchers spent a year meticulously measuring the gut flora of the heavier volunteers as they tried to lose weight by eating low-calorie diets, they actually discovered that the proportion of Firmicutes in their digestive tracts rose and the proportion of Bacteroidetes fell.  This discovery could easily explain why it becomes harder and harder to lose weight through dieting.

Think about this.  The same bowl of pasta yields a different number of calories for each eater.  Rodents raised in a sterile environment and lacking in gut flora need to eat 30 percent more calories just to remain the same weight as their normal counterparts.”

The first interesting thing from the quote above is that the relative proportions of various types of bacteria are impacted by our greater physiology.  I have suspected for years that a reduced metabolic rate and reduced core temperature (as seen with dieting) make it more favorable for firmicutes to inhabit the intestines.  There could be other changes to the intestinal ecosystem in terms of pH and other factors that takes place during low metabolic conditions.  I would assume so at least.

An even more interesting mention from the post above is that sterile guts require that rodents eat 30% more calories to maintain weight than a normal rodent with lots of gut bacteria.  This is interesting because the researcher I hold in the highest regard, Ray Peat, just so happens to believe that gut sterility is a beautiful thing – and has been writing about the ill effects of endotoxin for ages.  Endotoxin, a bacterial by-product, is assumed to “turn fat genes on” according to this recent study released (with other negative actions as depicted in the graphic on the right).  Peat talks about other mechanisms, most notably that endotoxin and bacterial proliferation in the gut leads to a physiological chain reaction that suppresses metabolic rate…

1) Bacteria proliferate

2) Irritation and fermentation in the gut from bacterial proliferation and endotoxin release increases serotonin production in the gut (where most serotonin is manufactured)

3) Serotonin is extremely anti-metabolic (it’s the hibernation hormone), and has a known connection with many aspects of metabolic syndrome such as obesity, diabetes, and hypertension – as well as disorders such as autism, schizophrenia, asthma, and more.  You can read more about serotonin in my post entitled The Sadder Side of Serotonin.

But a huge question remains because there are two major schools of thought that seem to be in conflict…

One school of thought suggests that certain foods feed “good bacteria.”  I talk about this at length in Diet Recovery, as resistant starches (from starchy foods, beans, whole grains, legumes, chilled starchy foods, Mr. Bean) and foods that don’t fully digest feed “healthy” gut bacteria, resulting in the production of the most metabolically-stimulating of all fatty acids – butyric acid (and other short-chain saturated fatty acids – SCFA’s, thought to generally have a positive health impact).  This more than amply explains some of the metabolic effects observed from studies on high fiber diets.

While Peat might acknowledge some benefit here, he seems to believe that there is an even better strategy at addressing this problem – and suggests we eat highly digestible foods that digest completely before they reach the digestive tract, while also eating raw carrots – a food that has an anti-bacterial property that can supposedly help to sterilize the gut (carrots are roots that live in the dark, wet dirt where they must protect themselves from bacterial invasion and have thus developed antibiotic properties).

I don’t have any definitive answers here.  I’m also wise enough to know that both strategies (highly indigestible/high residue vs. highly digestible/low residue) probably have their upside and their downside.

For those who have eaten both a really high fiber, whole foods, low-glycemic diet (beans, root vegetables, vegetables, whole fruits, raw greens, raw nuts and seeds) and have also tried eating a diet comprised of more refined, fast-digesting, high-glycemic foods  (white rice, white flour, juice, soft drinks, ice cream, etc.) – what have you noticed?  What seemed to help you achieve the goal of a higher metabolic rate?  Which left you feeling better and alleviated the most health problems? Which had a more favorable impact on bodyfat levels beyond about the 6-month mark?

In my experience, a highly digestible diet has been more of a star performer.  I assume this is because more calories are absorbed and used, and fewer are excreted out incompletely digested.  It’s also due to the fact that softer, refined, low-fiber foods are more calorie dense and palatable, leading to a naturally higher calorie intake.  After all, nothing raises metabolic rate like a surplus of calories.  But I’ve seen the opposite occur as well, and suspect that eating less refined foods may very well speed the passage of food through the gut and lead to less, not more, bacterial proliferation in the gut.  And even if there was more bacterial proliferation, could these foods actually selectively feed the desirable bacteria while eliminating the types of bacteria thought to trigger obesity-proneness?

What do you guys think?