The authors of this study wanted to investigate the toll very different diets have on the diversity of our gut microbiome. We’ve all probably heard the staggering estimation that we are home to around 100 trillion bacterial cells, a huge proportion of which live in our gut and are thought to be the cause of (or contribute to) the onset of diseases, such as obesity and inflammatory bowel disease.

**Before we dive into this one, I am just giving a general consensus of this article. There is A LOT of information here, so I just wanted to focus on the main ideas**

The researchers set up the study by comparing an exclusively planted-based diet to an exclusively animal-based diet. The plant-based diet was rich in legumes, grains, fruits and vegetables (~22% fat and ~10% protein), whereas the animal-based diet consisted of meat, eggs and cheese (~70% fat and ~30% protein). I know what you’re thinking, these are extremes (polar opposites one might say), and I think that was the purpose. They wanted to investigate what the effects of two completely different diets were on the gut microbiome and how quickly these effects took place.

The subjects of the study (both men and women) were subjected to five days of each diet with six days post-diet for follow-up analysis. After each diet, the participants were allowed to return to their previous way of eating (called a washout) before they were subjected to the other diet. Essentially their guts were allowed to go back to their ‘normal’ or baseline state. Each subject participated in both the animal- and plant-based diet. This allowed researchers to account for individual variances during each diet phase.

In the animal-based diet, researchers observed a significant shift in the gut microbiome of each individual after just one day, and saw that the gut microbiome returned to its original state two days after the subjects returned to their normal ways of eating.


Genetic analysis of the different types of gut bacteria showed that animal-based diets resulted in a decrease in diversity when compared to each individual’s baseline (or starting) measurement. Specifically they noted a decrease in the bacteria that aid in the processing of fiber and an increase in bacteria that aid in the production of bile which is thought to contribute to diseases such as inflammatory bowel disease. They also observed a shift in the gut microbiome metabolic activity. There was a decrease in carbohydrate fermentation associated bacteria and an increase in the amino acid fermentation associated bacteria in the animal-based diets compared to each individual’s baseline.

Interestingly, the animal-based diet had a greater impact on the gut microbiome than the plant-based diet, although, on the plant-based diets, individuals did lose a little weight.

Okay, my take on this:

First and foremost, this is not an animal vs plant study. This is the study between two very different methods of eating and their effect of gut microbiome diversity. What the researchers did note is that the shift in the gut bacteria did resemble a herbivorous vs carnivorous microbiome in the plant-based and animal-based diets, respectively. Which I thought was pretty cool. Science works. Science is predictable.

So what does this mean? There is so much still left to study on this topic (and so much more research I could report on, such as the gut-brain axis and its effect on a person’s psychological state. WHAT!?), but the take-away from this study is simple: you literally are what you eat.

While I don’t condone a solely animal-based diet OR a low-protein, plant-based diet, I do endorse a diet that consists of a wide variety of foods that help contribute to a healthy gut. If you choose to eat meat, THAT’S FINE, but make sure you’re getting in a variety of fruits, veggies and grains to keep your gut healthy (side note: anyone know someone who complains that when they eat veggies their stomach gets upset? This could explain why. They simply don’t have the microbiota present to digest the plants properly, so they don’t feel great. Then their solution is to not eat the veggies anymore, when in reality they need to keep exposing their gut to these foods to cultivate the proper bacteria to digest their veggies).

If you choose to follow a plant-based diet, make sure you are also eating a good variety of fruits, veggies and grains. It is so easy to eat highly processed fake meats as a protein source, but you’re better off trying to incorporate non-processed proteins…for your gut’s sake. But also make sure your protein intake is higher than reported in this study. We are athletes after all.

What do you ladies think? I love reading about how something simple as bacteria in your gut can influence how your body functions, your psychological state and your health. It’s wild, and I’m here for it!


Ready to invest in your nutrition and learn how to eat for performance and strength? Find out more HERE.

Learn how to use carbs to properly fuel your training HERE.


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