11 January 2016

Is calorie counting over?

We are not all equal when it comes to food. We’ve known this for a few years now, some people are just not equipped with the best genes. However, it seems that we may have missed a major player in the digestion equation, namely our microbiota.

Our gut microbiota have a formidable secondary role in extracting energy from food that ends up undigested in our gut.

Having passed through the small intestine, it is then our microbes’ turn to chew leftovers and extract as many calories as possible from them for their, as well as for our, benefit.

But, knowing that microbiota species identities are different from person to person, is extracting calories from food a unique and tailored process for each one of us?

food

Indeed, some of these micro-organisms are just better than others. Peter Turnbaugh was a PhD student when he conducted an experiment on mice that would change the way scientists think of calories-in/calories-out:

What he did was simple enough, he transferred the gut germs of obese mice into lean germ-free mice (let’s call them Batch O), he also transferred the gut germs of normal lean mice into lean germ-free mice (Batch L). He then fed Batch O and L with exactly the same food. Two weeks later, Batch O had gained a lot more weight than Batch L. Since he used recipient mice with no germs that could influence the results, the effect was directly linked to the germs from obese mice (see figure, excuse the mice's coat colours please).

Turnbaugh's experiment in 2006
Turnbaugh calculated that Batch O was getting 2% more calories from food because the germs from obese mice were better at extracting energy. For each 100 calories Batch L would get, Batch O would get 102 calories. Not much of a difference but think about it in the long-term: it all adds up!

Other experiments have been conducted in humans that reach the same conclusion:

It is our gut microbial content that determines how much energy we extract from food – Do you want to tweet this? 

This has some serious implications, imagine food labels for example: a 145 calories chocolate cookie may mean 148 for someone with an unfortunate set of gut bacteria super good at extracting energy.

This said, the set of microbiota that we are hosting is directly influenced by our day-to-day dietary habits. For example, someone who is not used to eating fats will not harbour the germs that are good at extracting energy from it, so the fat will go through undigested; whereas someone who’s used to a high fat diet, has the ‘right’ set of germs to deal with fat and get the most out of it.

Effectively, it means that the odd cookie won’t affect a no-cookie diet person the way it will affect a cookie lover who indulges frequently in cookie eating.

But this is only the first step, calories in. Calories out is the next step.  All that energy that has been kindly extracted by our microbiota needs to have a purpose: either it is used immediately, or it is stored away for later use.

But that is another story…

Are you a calorie counter? Will you change your attitude towards food labels?
I’d love to read your thoughts, feel free to leave me a comment, I’d love to read them.

The fascinating results from Peter Turnbaugh were published in the famous Nature paper in 2006 (yep, and we’re only catching up now!). Although it is unfairly hidden behind a pay wall, you can read its abstract here.

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My bugs and I Published @ 2014 by Ipietoon