My weight’s been bugging me

Dieting hard and not getting any slimmer? Your nighbour eats two pizzas a day and is skinny while you only have to smell cheese to put on weight?

You’ve probably blamed your metabolism. And it might well be at fault (as might the exercise you just never get around to). But it could also be bugs.

Y es, bacteria. Inside the average human gut live 10-100 trillion bacteria – many more bugs there than there are cells in the human body. Just like those inside ruminant animals, they help you to digest food. The more efficient they are, the more nutrition you take in. Indeed 10% of your calorie intake may come from gut bacteria digesting complex sugars for you.

Mice living in sterile conditions, with no gut bacteria can eat way more mouse chow and stay thin than their bacteria-filled counterparts. Indeed those with bacteria put on 42% more body fat over the course of one experiment despite those with no bacteria eating 29% more food. Take the bacteria free mice and give them a “normal” intestinal flora and sure enough within two weeks they pack on body fat and increase insulin resistance (despite restricted food).

So maybe instead of berating your metabolism, announce prodly that you have efficient symbionts.

ReferencesBackhed F., Ding H., Wang T., Hooper L.V., Koh G.Y., Nagy A., Semenkovich C.F., and Gordon J.I. (2004) The gut microbiota as an environmental factor that regulates fat storage, PNAS, 101(44): 15718 – 15723.

Cummings JH, Macfarlane GT. (1997) Role of intestinal bacteria in nutrient metabolism., J Parenter Enteral Nutr. 21(6):357-65.
Ley R, E. Backhed F., Turnbaugh P., Lozupone C.A., Knight R.D., and Gordon J.I. (2005) Obesity alters gut microbial ecology PNAS 102(31): 11070 – 11075.

Nicholson J.K., Holmes E. and Wilson I.D. (2005) Gut Microorganisms, mammalian metabolism and personalized health care, Nature Reviews Microbiology 3, 431-438.

Xu J. and Gordon J.I. (2003) Honor thy symbionts PNAS, 100(18):10452-9.



Filed under Curious Science, Science

3 responses to “My weight’s been bugging me

  1. This is curious because antibiotics are routinely used in raising livestock and poultry to make them gain weight faster. And I’ve never heard of people gobbling antibiotics to lose weight, and people will do just about anything to lose weight without all the trouble of diet and exercise. How do these reconcile with this research? I don’t know enough about the subject to even guess.

  2. Antibiotics are given to animals to prevent them from getting and spreading bacterial illnesses (in high density farming as in chicken and cattle production, illnesses spread fast and can cause the death of a number of animals), not directly to make them gain weight.

    Though it does make me wonder whether they are a little counter-productive. I might look to see if studies have compared weight gain in animals given antibiotics compared to those not.

    As for people trying to lose weight. I guess it’s a new realisation. Or perhaps as antibiotics are prescription-controlled people are less willing to talk about the reasons for taking them and already are gobbling them.

  3. Pingback: My weight’s been bugging me cont….. « Quarks, Quirks and Quips

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