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  • Writer's pictureMichelle Mohan

How Your Gut Microbiome Influences Energy Balance

Updated: Oct 20, 2023

If weight loss is one of your goals, I have a super interesting study to share with you to start your month. One of my personal mentors, Dr. Will Bulsiewicz, MD emailed this study to me and I’m excited to share it with you all.

Are you ready to get into it? Okay, let’s do this!

Nature Medicine 🌿 🌿 🌿

Host-Diet-Gut Microbiome Interactions Influence Human Energy Balance:

A Randomized Clinical Trial

✍️ Corbin, K.D., Carnero, E.A., Dirks, B. et al. Nat Commun 14, 3161 (2023).

What they studied:

This study examines how the gut microbiome influences energy balance in the human body.

The researchers used a controlled environment where 17 subjects were admitted to a metabolic ward, effectively a dormitory where the researchers had complete control over what they ate. 😮😮😮

The study design was a randomized crossover (everyone received both diets) involving young (~30 years old), healthy, weight-stable (BMI 25.1 on average) males (9) and females (8) with normal bowel movements at baseline (82% had Type 4 Bristol stool BMs, which are the glorious and highly sought after normal BMs). Their baseline fiber intake was typical of most Americans, taking in 7.6 grams of fiber per 1000 kcal of intake. The recommended amount is at least 14 g per 1000 kcal.

For 23 days each, the participants were given a Microbiome Enhancer Diet (MBD) and a Western Diet (WD). The microbiome diet had four main characteristics that made it good for the gut: high in dietary fiber, high in resistant starch, large food particle size, and limited ultra-processed foods. (Sounds reasonable.) Both diets provided the same number of calories and the same proportion of macros.

The main outcome the researchers were interested in was how the MBD versus a WD would affect the amount of energy available for the body to use. Secondary outcomes included levels of hormones related to digestion, feelings of hunger and fullness, and food intake.

What are the headline findings?

The results show that compared to the Western diet, the Microbiome Diet led to a significant daily loss of energy through feces, meaning they were channeling 116 calories per day into their bowel movements instead of absorbing those calories. Translation: They were having epic weight loss dumps!

Despite this, there was no change in the amount of energy the participants expended, their feelings of hunger and fullness, or their food intake.


What the study really showed:

Here’s what you need to know...

First, the Microbiome Diet caused significant changes to the gut microbiome, as shown by:

➡️ An increase in the amount of microbial DNA (more microbial DNA with the MBD).

➡️ A change in the variety of microbes present (beta-diversity) and more specifically the MBD enhanced the growth of 6 fiber degraders/butyrate producers while the WD enhanced the growth of 4 inflammatory microbes that love sugar (the bottom 4 below).

➡️ There was an increase in the production of short chain fatty acids – butyrate, acetate and propionate – on the MBD. Note that both stool and blood SCFAs levels increased on the MBD diet. Let’s go, fiber and resistant starch! Woooooo!!! ( I also want you to know that butyrate stimulates GLP-1, which is why Ozempic works for weight loss).

Second, the Microbiome Diet led to a statistically significant weight loss and a trend towards more fat loss during this short study where they were eating the same number of calories!

Third, personalized nutrition strikes again! On the Western diet, there was very little variation in the percentage of ingested calories that were absorbed, ranging from 94.1 - 97.0%. In other words, when you eat a Western diet, regardless of who you are, you’re going to be absorbing all those calories. BUTTTTT… on the Microbiome Diet there was wide variation in the percentage of ingested calories that were absorbed, from 84.2–96.1%. This means that on the Microbiome Diet, people were pooping out anywhere from 73–390 calories per day.

Was this variance due to differences in the microbiome? The answer was yes.

The two most important predictors for excretion of calories were the amount of SCFAs and the amount of microbial DNA in the poop.

They also found 16 specific microbes that were more prevalent among those who were shedding calories in their poop. Among these 16, there were 4 that were immediately recognizable because they’ve previously been seen as more prevalent after bariatric surgery or calorie restriction.

Notably: No bariatric surgery or calorie restriction is required to get these microbes! You just need to consume more fiber and resistant starch!

Lastly, they found that on the microbiome diet, participants were getting literally DOUBLE the amount of SCFAs in their blood and twice the percentage of their calories from SCFAs.

So in other words, they were absorbing less calories but twice as many SCFAs while on the Microbiome Diet.


What you should do about it:

In this study they found that on a Microbiome Diet people were releasing more energy in their poop. This was not undigested food, but actually due to the fiber loving microbes that were actively creating a sh!t ton (sorry, couldn’t resist) of SCFAs.

You get proportionally more energy from SCFAs (this is a great thing), but you also poop out more energy so you’re actually absorbing less overall. This also explains why numerous studies, both population research and clinical trials, have indicated that fiber helps people lose weight (in addition to reducing their risk of heart disease, cancer, diabetes, etc.)

The bottom line is that for metabolic health, we should be opting for a higher fiber diet mixed with a variety of plant-based fibers and resistant starches.

So a big shout out and thank you to my hero, Dr. Will Bulsiewicz, MD, a New York Times bestselling author of Fiber Fueled, my fiber bible, for sharing this study with me today.

Wishing you all a month filled with yummy FIBER and epic caloric dense dumps! 💩😂

Michelle Mohan NBC-HWC, CNWE

Board Certified

Nutritional Diagnostics & Gut Health Specialist


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