Your gut and the microbes within - Australasian Society of Lifestyle Medicine

It’s called the microbiome and it refers to the mix of families of microorganisms that exist in your gut. So what you might say. Do I need to know that? Scientists didn’t think so until a few years ago when they noticed that the mix of microbiota, or miniscule organisms in the gut seemed to change under various conditions. The ratio of the two major families (and there are thousands of these), known as Bacteroidetes and Firmicutes, which together account for around 75% of the microbial community, seemed to be different in obese, as compared to normal weight humans. This suggests that the ratio might change as weight is gained. So what might this do to the body as a result of such a change?

The gut and microbiota

Let’s first set the stage: Microbiota are ‘microscopic living organisms’ that exist throughout the body. There are several trillion of these making up a couple of kilos of body weight in total, many of which live happily in our gut and intestinal tract. In fact, over a third of the ‘stuff’ making up our faeces is actually microbiota! Like us, they eat, produce energy, have sex (or at least divide into offspring), pass out waste and die. Most are our ‘little friends’; they need us, and we need them. Over millions of years of evolution our immune system has gotten to know them, and hence opts to leave them alone. Under normal circumstances, gut microbiota are responsible for several important functions in our body:

They ’harvest’ extra vitamins, minerals and energy that can’t be obtained by our own digestive processes from food, and would otherwise be lost in faeces
They make some of the vitamins we need to survive, for example vitamin K
They help stop parasites from making their home in the gut, by “squatting” or “squeezing” them out

Things can go wrong though. The normal mix of ‘friendly’ and ‘unfriendly’ little critters is not set in stone and the balance can sometimes tip. In a situation, called ‘dysbiosis,’ Lactobacillus bacteria.

Effects on energy

Given all of the above, what are the effects on our typical energy estimates? It should be apparent that giving a food an energy value – say 100kcalories for a piece of cake – has little relevance to the effects of this on the body. One person’s biome might make mince meat of this, resulting in only 50 kcalories having any effect on energy or body fat. Another person’s little friends might gulp the whole lot down and store it all as fat. Thus, the energy balance equation (weight = calories in minus calories out) used by most popular magazines and just about every weight control book written should be seen as a static ‘physics’ equation. In a living organism a ‘systems’ approach is necessary because of everything that goes on between the ‘energy in and energy out’. A calorie therefore is no longer is a calorie. And the 2nd law of thermodynamics should no longer be seen to the full answer in a biological system.

Implications?

This suggests that a change in the microbiome favouring obesity is likely to have its own ‘legs’. Once it has occurred it may take a lot of effort to change back. On the positive side, a big change to a healthy diet over time could mean a protective change in the biome that makes it easier to keep that weight off over time. And what of the ‘no effort’ approaches to modifying the biome? Of course medical researchers are looking for the ultimate drug or chemical mix to do this. Alternative health practitioners have been promoting ‘pro-biotics’ as a means of doing so, although with little evidence of the mix of ingredients required. Still, sales are on the up and up. One thing is for sure. The gut has now hit the (scientific) fans. You’re likely to hear a lot more about it and its role in health and weight control in the future – at least until we find another part of the anatomy that stirs the scientific pot more vigorously.

Do new gut findings explain why ‘obesity could be in the air?’

Avid readers of this esteemed tome will remember a lead story in the winter edition of 2011 discussing how chemicals in the environment have been implicated as possibly causing obesity. It was concluded that such a phenomenon could occur through changes in endocrine organs affecting the brain’s appetite mechanisms. New findings on gut microbiota are now beginning to provide a more likely scenario. Environmental chemicals (there are more than 80,000 of them since the industrial revolution) could get into the gut via food or drink, thus altering the microbiome in favour of greater fat stores. Such chemicals could throw out the existing balance of ‘happy little friends’, just as with a new, or changed food source.

Of mice and guts

In support of the above, recent studies have shown that:

(a) ‘Germ free’ lean mice that are raised in sterile conditions with no resident gut microbes take on the microbiomic structure of obese ‘conventional’ mice if living in the same cage

(b) Injecting gut micro-flora from obese mice into lean mice can make the latter fat, suggesting that the gut microbiome can change the fate of food in the diet

(c) Injecting the ground faeces of healthy humans into the gut of people with gut problems (Chrone’s disease, irritable bowel syndrome etc.) can improve these conditions, presumably by changing the gut microbiome.

Your gut therefore, could be more than just meets the eye – and that’s just the inside of it.

This article first appeared as a feature article in Professor Trim’s Waistlines Issue No. 28, 2012.

Acknowledgement of Country

The Australasian Society of Lifestyle Medicine acknowledges Aboriginal and Torres Strait Islander peoples as the Traditional Custodians of the unceded lands and waters where we live and work. We celebrate their ongoing connection to land, sea and culture and pay our respects to Elders past, present and emerging. As a bi-national (or Australasian) society, we also acknowledge ngā iwi Māori as the Tangata Whenua (or people of the land) of Aotearoa. We are committed to upholding the principles of the Te Tiriti o Waitangi, building our relationship with Māori, and working together to improve the health of all First Nations peoples.

The gut and microbiota

Effects on energy

Implications?

Do new gut findings explain why ‘obesity could be in the air?’

Of mice and guts

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