Podcast Episode 183 – Gut Health and Weight Loss

Key Topic

There are clear links between gut health and overall body weight, on average. It’s not a debated fact that there are common trends.
The more complex topic is 1) How much of it is linked? 2) Does implementing gut health specific nutrition directly contribute to weight loss? and 3) Does losing weight change gut health by itself and/or is it just that the behaviours involved in that process influence gut health?
Gut-health kind of has two separate definitions with a bit of overlap:
1) One way people define it is a lack of symptoms related to things like bloating and other IBS-type symptoms.

2) The other way is based on the populations of bacteria living in the microbiome and trends associated with that.

In this episode, we are largely referring to that latter description.

Interesting Studies On the Topic

Study One

Study 2

‘The famous mouse study.’
Basically, they concluded using faecal transplants that add the microbiome from somebody with obesity to somebody without.
Could have the potential to contribute to obesity in the new person even in the same environment.
Which again, is a bit of an insane thing to occur.

Study 3

Two groups were separated by their microbiome characteristics and given the same diet.
One group had more Prevotella and the other had more Bacteroides.
The group with more Prevotella lost 3.5kg more fat.
Studies like this have been used to promote personalised nutrition. But that is a bit of a speculative link at this stage.
As a side note, if research consistently found this, it’s more of a prediction of the rate of weight loss rather than indicating different dietary approaches are superior for different microbiomes.

Overall, there’s a long list of interesting studies, but we just wanted to touch on a few.

Some Explanations

We know that calories in vs calories out has to play a role. I think we’ve talked about that enough to not need to explain that again.
SO for there to be a link, there needs to be influences on calorie intake and/or calorie expenditure.
One tweak I’d add on the calorie intake side is that we can extend that to calorie absorption.
One example is that fibre contains calories that we can’t digest. But some of those calories can be digested by bacteria in the gut. So that’s a small factor.
Similar applies with other foods. An example I often talk about is how we typically absorb 70-80% of the calories in almonds. One person might absorb more than another.
Interesting note: Some people have highlighted that improving gut health might improve absorption which could LEAD to weight gain. But research hasn’t supported that thought process.
Changes in appetite regulation. Gut bacteria can influence hunger and fullness hormones, which could change intake, even within the same environment.
There are some explanations for how it could influence energy expenditure, but I haven’t seen any solid succinct explanations that I think are worth sharing. But it’s worth considering that this could be relevant.

Interpreting The Overall Body of Research

There clearly is a link. The bigger question is how much does this matter and what aspects are practically relevant.
I’ve never seen any individual approach significantly outperform what you would expect based on other models of weight management involving calories.
So clearly it is not the be all and end all.
This might be a poor example, but pointing to one thing: When probiotic supplements are studied and weight is a factor measured, every now and then we might see a 1kg fat loss difference. But it’s rarely a significant difference.
On another note, we consistently see high-fibre intakes being linked with lower body weights.
But this is also explainable by reduced calorie intakes due to satiety AND also often choosing foods that are less calorie dense too.
So that is focusing on specific interventions. But similarly with dietary patterns that are linked with better gut health – in the cases where weight loss is relevant, they typically also involve a reduction in calories.
If pointing to the hormonal changes in relation to gut health, that might make sense, but even the changes in intake could be explained more directly with fibre and food volume.

Summary

In a way, even without clear information on how much this matters, the next steps are very clear.
Step 1: Keep the basics in mind. Have an awareness of calories. This doesn’t necessarily mean tracking. It just means don’t ignore calories to solely focus on gut health.
Step 2: Do the things that are good for gut health. At a minimum this will be good for general health anyway.
To do this:

1) Aim for >30 different plant based foods per week.

2) Have a good intake of dietary fibre.

3) Probiotics are an option. It likely makes sense to regularly include some form of fermented foods that are high in probiotics.

4) Prioritise a wide variety of nutrient rich, minimally processed foods.

Relevant Blogs/Research

Relevant Studies: