High fat diets and your gut microbiome

Recent research has highlighted high fat diets can alter the composition of microbes in the gut in a negative manner.

Research about high fat diets

In a study in 2019 researchers tracked a group of 217 people split into 3 groups where participants ate 20%, 30% or 40% of their calories from fat over 6 months.

The levels of protein and fibre stayed the same in all groups.

The effect of high fat diets on the gut microbiome

The group with lowest levels of fat had an increase in short chain fatty acids (SCFAs). These are metabolites produced by the gut bacteria when they consume fibre. SCFAs are important for our gut health because they provide fuel for the colon cells and help to reduce inflammation. 

It’s interesting that the group with the most fat had decreases in microbes which produce the SCFA, despite no changes in fibre intake.

So despite eating the same amount of fuel for the gut bacteria, they produced less SCFAs. 

The role of fat in health

You might be thinking we need to reduce all fat, but this doesn’t mean we don’t need any fats in our diet. 

We really do need healthy fats, like those from avocado, oily fish, nuts and seeds and olive oil. Fats are important for our brain function, absorbing key vitamins like vitamin A, E, D and K, as well as supporting healthy cells and skins.

What about the keto diet?

If you’re someone who majors on high fats and proteins, with no or low carbs you might want to think about your long term gut health. I’ve written a longer article about the keto diet and IBS with more details, but essentially your gut microbes don’t appear to do well in a high fat environment.

The beneficial microbes and their healthy metabolites don’t appear to thrive in a high fat diet, even if fibre is still present. 

A high fat diet can also contribute to a leaky gut by opening the gap between the intestinal cells to allow toxins from bacteria into the body. 

Another reason why I don’t recommend diets such as keto or carnivore for people with IBS is that strict diets eliminating whole food groups should only be carried out under the supervision of a trained nutrition professional. It’s easy to miss important nutrients if you haven’t thought about the big picture of your diet.