Updated 18 February 2015

Could 'poo transplants' help us lose weight?

'Faecal transplants' can clear up nasty infections, and CyberShrink wonders if this procedure may also inadvertently cause people to lose or gain weight.


Sometimes a really odd headline catches my attention. Until I spotted this one, I had been unaware that there were bold surgeons out there carrying out faecal transplants.

A highly specific condition

Yes, indeed, in certain situations, doctors may transplant poo – giving you something more unusual to add onto your organ donor card. Don’t worry, though, it won’t transform you into a politician or make you more “full of it” than usual.

Such transplants are only done very rarely (strange, considering the abundance of material), for a highly specific condition – the result of a nasty infective agent called Clostridium difficile, which can  cause chronic diarrhoea, colitis, cramps, nausea and dehydration, and can be really difficult to clear up.

The condition can arise as a side-effect from taking antibiotics. Recurrent infections with this organism are notoriously difficult to treat, and using heavy amounts of antibiotics can be ineffective and further complicate the situation.

A method currently being tested is called “faecal transplantation”. This involves a sample of faeces being taken from a healthy donor and, by means of a catheter, placed into the colon of someone with the infection. Alternatively, it may be inserted, using a thin tube, through the nose, into the small bowel below the stomach. 

It’s believed that this simple intervention can restore the normal balance of bacteria that usually live within the digestive system, those from the healthy donor replacing those causing the disorder.

Read: Bacteria vital for keeping intestinal lining intact

The procedure seems to work in over 90% of cases, however unappealing it may seem. A more recent variation on the method has been called “poo in a pill”, and involves capsules containing frozen faeces, and this also seems effective. A recent trial of 20 people, where each patient was given a series of 30 capsules containing gut bacteria from four healthy donors, seems to have succeeded in 18 out of 20 cases, without side-effects.

An obese donor

But here’s where it gets more interesting. Could obesity be, at least in part, an infectious disorder? This month, a case was reported of a woman, with repeated Clostridium difficile infections, who was treated with a faecal transplant from an obese donor. And she rapidly gained weight after this, becoming obese herself!

Until the significance of this report is clear, it would be best to avoid using overweight donors until it is established what role the bacteria in your gut may play in your general metabolism and health.

Read: Gut bacteria suffer when hit with infection

This 32 year-old lady’s weight had been stable at 61.7 kg, with a BMI (body mass index) of 26, and she’d always been of normal weight. The donor used was her teenage daughter, otherwise healthy but really overweight. 16 months later, her weight had gone up to 77.1 kg, with a BMI of 33, meeting the medical criteria for obesity.

Even on a medically supervised liquid protein diet and an exercise programme, she remained obese.  Despite continuing to diet and exercise, she remained overweight, and after 3 years weighed 80.3 kg, with a BMI of 34.5 

One has to wonder whether in some way some of the donor bacteria, though they cleared up her chronic gut infection, may have produced a negative over-all impact on her metabolism.

Notable increase in weight

This is not as far-fetched as it might sound, as earlier research in animals found that when gut bacteria from obese mice is transferred into mice of normal weight, it may cause a notable increase in weight. Exactly what component in the gut of fat animals causes this effect is not known.

Maybe other factors were responsible for this woman’s weight gain, such as the resolving of her chronic infection, genetic factors just happening to come into play at this time, or something else.  But she had never in her life been over-weight until she received the stool transplant.

As usual, a major conclusion here, like in most studies, is that much more research is needed.  We need to know more about the range of gut bacteria and the role they play. If the ones that are beneficial can be identified, they could be grown to benefit our health. 

Read: Food allergy-preventing gut bacteria discovered

We tend not to take seriously the large eco-system of bacteria and viruses which normally live peacefully in our guts.  They probably play a significant role in how we digest and process the food we eat.  And some combinations of such micro-organisms may predispose us to obesity.  It’s not as simple as naturally skinny people think – obesity is not entirely a matter of diet and exercise.

People on similar diets and exercise regimes don’t lose or gain the same amounts of weight. It seems that there are populations of organisms that predispose us to weight-gain, especially when our gut has been sterilized by antibiotic use or the presence of hostile germs. 

Is it possible that there could be more wholesome populations of gut bacteria living within naturally skinny people, helping them to remain thin, which could be transplanted into fat people, and help them lose weight in a safe and natural way?

Read more:

Faecal transplant may help with bowel disease

Faecal transplant may help relieve C. diff diarrhoea

Synthetic 'poo' may cure infection

Image: Human digestive system from Shutterstock


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