The Best Type of Fiber for Weight Control?
This Week’s Research Highlight
Beta-glucan is linked to healthier body composition and better glycemic control — perhaps through shifts in gut microbes and physical activity patterns.
We've long recognized that fiber affects appetite regulation and metabolic health. However, we also now know that there are many different forms of fiber, and each of them do not affect the body in quite the same way. Which one could be said to be the best?
To explore how various fibers affect metabolic homeostasis, researchers at the University of Arizona performed an experiment with rodents that were fed a high-fat diet.
They allocated the mice into five groups, and supplemented their diets with five fiber types:
- Pectin
- β-glucan
- Wheat dextrin
- Resistant starch
- Cellulose
Each of these fiber types naturally occur in various plant foods. For example, pectin occurs abundantly in apples and citrus fruit. But most importantly, each of these fibers has distinctive physical characteristics (including their solubility, fermentability, and viscosity) which may influence their impact on the gastrointestinal system and downstream health effects. Each of these fibers, in separate experiments, have been shown to affect food intake and metabolic health to varying degrees, but no study (until now) has ever directly compared all of them to determine which might be most effective.
All of the mice were fed their respective diets for 18 weeks. To assess how the diets were affecting the mice, the researchers monitored their weight as well as their body composition (lean mass and fat mass). They also assessed the rodents' glycemic responses after eating, and analyzed their gut microbiota.
At the end of the 18-week study period, some clear differences were observed.
Let's start with the body mass data. Recall that all of these mice were on a high-fat, high-sugar diet — literally designed to drive weight gain. So all of these mice were going to get fatter over the course of the study, to varying degrees.
But you can see from the graphs below, one fiber type really stood out from the others in this respect. For one thing, the rodents that ate the diet supplemented with β-glucan gained significantly less weight, compared to the other fibers.
Even better, when the researchers examined their body composition, they found that the β-glucan group not only gained far less body fat, but they were also able to maintain more lean mass. Which, of course, is generally what you want — more muscle, less fat.
The β-glucan group was also more insulin sensitive. In response to a glucose tolerance test, their blood sugar levels rose less than the other groups, and insulin concentrations were lower after being administered the glucose load (indicating that their bodies needed less insulin to dispose of the sugar).
At first glance, these metabolic findings are impressive, but also kind of mysterious, because there were no significant differences in caloric intake between the fiber groups. So what exactly was going on here?
Interestingly, it seems that the β-glucan group was exercising more. The researchers had the foresight to track energy expenditure and the total distance that each rodent traveled within their cages, and they determined that the β-glucan group was running a lot more than their counterparts.
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That could certainly explain the reduced weight gain as well as the improved glycemic control. But why would a fiber supplement affect physical activity patterns?
The analysis of the rodents' microbiota provided a key clue. Mice that were fed β-glucan generated greater amounts of butyrate in their gut, in contrast to the other fiber groups.
When fibers such as β-glucan are consumed, specific gut microbes nibble on it, and during the fermentation process they generate short-chain fatty acids, including butyrate. β-glucan is a highly fermentable fiber, so it makes sense that it would alter the composition of the gut microbiota in this way.
Now, butyrate does all kinds of beneficial things within the body. For instance, it binds to receptors in the gut, triggering the release of GLP-1 and other peptides involved with appetite regulation. It's also linked to boosted insulin sensitivity.
But here's the interesting part: short-chain fatty acids have also been linked to physical activity and athletic performance. Speculating a bit here, I think that this might have been playing a role in the findings described here. Prior trials in humans have revealed that elite runners carry greater amounts of a specific genus of bacteria, Veillonella, in their guts, and further exploration using animal models demonstrated that this type of bacteria enhances exercise performance via production of short-chain fatty acids. And although this research team didn't look for Veillonella, there is good reason to believe that β-glucan does fuel this particular genus of bacteria, more than other forms of fiber.
If you're looking to add more β-glucan to your own life, they can be found in cereal grains like barley, oats, and rye, as well as seaweed and mushrooms.
Random Trivia & Weird News
The teeth of Komodo dragons are coated in iron.
Komodo dragons are the largest lizards in the world, tipping the scales at more than 350 pounds and growing more than ten feet long. They are also ferocious predators, killing almost any prey they stumble upon — including, in a few cases, humans — with their venomous bite. So these creatures fully live up to their name.
But a new discovery makes them seem even more legendary. Researchers noticed some time ago that the serrated edges of the reptiles’ teeth were covered in an orange pigment. Closer inspection revealed that the enamel contained concentrated iron. This attribute, no doubt, would keep the teeth sharp and maintain their durability across their life.
Photo credit: Charlotte Ellis, Zoological Society of London.
Podcasts We Loved This Week
- Ted Schaeffer: The relationship between testosterone and prostate cancer, testosterone replacement therapy, and tools for predicting cancer aggressiveness and guiding therapy. Via The Peter Attia Drive.
- Garriy Shteynberg: Sharing that moment — can collective experiences bring people closer together? Via The Conversation Weekly.
Products We Like
Bob’s Red Mill Oat Bran
Oat bran is the most abundant source of β-glucans in the diet, containing more than twice as much as the same volume of whole oats (the bran is where the β-glucan lives, basically). Oat bran has other advantages over oatmeal too: it has less sugar, more protein, more fiber, and it cooks faster.
Around three grams of β-glucan has been shown to elicit significant metabolic effects in humans. To hit that threshold, you will want to consume around 50 grams of oat bran in dry weight (or 100 grams of whole oats).
humanOS Catalog Feature of the Week
Optimizing Sleep
This week, we’d like to highlight our Optimizing Sleep course, a key module from our Daily Performance Program.
“If sleep doesn't serve an absolutely vital function, it is the greatest mistake evolution ever made.”—Allan Rechschaffen.
In this course, we take a look at sleep in the modern world, and the role of technology and lifestyle in contemporary sleep patterns. Particularly, this course zeroes in on how sleep affects facets of mental performance, such as attention, memory, decision-making, and emotion regulation.
For example, past research has shown that lack of sleep makes it harder for entrepreneurs to assess business ideas, and people with insomnia have a harder time focusing and shutting out distractions compared to people who sleep well. Finally, we go into some relatively easy things that you can do to get better sleep - starting tonight.
Wishing you the best,
