Toilet Paper

Obesity, Fiber, and Microbes in the Gut

Will freeze-dried poop pills play a role in the future treatment of obesity and related problems? It seems possible, but much work will go into providing a complete answer. New research in Nature Medicine offers tantalizing hints, though. In subjects with severe obesity, researchers tested the combination of fiber and a transplant of microbes in freeze-dried fecal capsules. Thus they found that the right kind of fiber – in combination with a fecal transplant – can yield better insulin sensitivity.

Fecal Capsules Plus Low-Fermentable Fiber

This was a small proof-of-concept study – only 70 test subjects. But it was randomized and placebo-controlled. Half of the subjects received freeze-dried fecal capsules from lean donors. The other half got placebos. Everyone received a fiber supplement. But half of them got highly-fermentable fiber. The rest got fiber that would not readily ferment in the gut.

It turns out that the type of fiber made a difference. Only the subject in low-fermenting fiber getting a fecal transplant had a benefit. Their insulin sensitivity improved significantly after six weeks. The other three groups saw either no improvement or a bit of worsening in this measure.

So these results suggest that a low-fermenting fiber might play an important role in the effect of gut microbes on metabolic syndrome and obesity. The senior author on this study, Karen Madsen, explained:

“When you transplant beneficial microbes, you need to feed them to keep them around. If you give a new microbe and you don’t feed it, if you continue to eat a diet of processed foods and no fibre, then that microbe will likely die.”

Much More Work to Do

These results are quite enticing. But as the authors note, this was a very small, proof-of-concept study. So it has many limitations. The intervention with fiber was only six weeks. After the fiber stopped the improved insulin sensitivity was gone within six more weeks. But the size of the study limited the ability to figure out exactly why. Nor could this study give us a full picture of the metabolic benefits of this intervention.

Madsen plans more and bigger studies to produce a more complete understanding.

Notwithstanding all of that, these results are quite encouraging. The complexity of the microbiome and its role in obesity is great. But researchers are getting a better handle on it every day.

Click here for this study and here for more from the University of Alberta, where the study was done. For more on fecal transplantation in obesity and metabolic syndrome, click here and here.

Toilet Paper, watercolor © Krystyna Prus Szczepanowski / flickr

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July 12, 2021