ot: Antibiotics may make you fat by altering gut bacteria

March 29, 2012

Antibiotics may make you fat.

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THE trillions of bacteria that colonise our guts are in jeopardy.

Overusing antibiotics has not only led to the development of dangerous

superbugs, but has changed the bacteria that live inside us. Now

evidence suggests that new gut floras may be responsible for our

expanding waistlines.

Antibiotic use has been rising for the past 70 years. They are now often

prescribed as a precaution for illnesses when the cause has not been

confirmed as a bacterial infection. Blaser, a microbiologist at

New York University, fears that over-prescribing antibiotics could be

harming some communities of " good " bacteria that line your intestines.

The effects could be long-lasting, too. For example, some antibiotics

seem to permanently oust /Helicobacter pylori/from their home in our

stomachs. Widespread use of antibiotics has correlated with a fall in

the number of people playing host to /H. pylori/. That might seem like

good news since the bug has been linked to stomach cancer and gastric

ulcers, both of which have become less common. However, these positive

outcomes coincide with a surge in cancers of the oesophagus, attributed

to the more acidic environment /H. pylori/ leaves behind when it vacates

the stomach

/Nature Reviews Microbiology/, DOI: 10.1038/nrmicro2245

To investigate whether overusing antibiotics could also play a part in

the rise of obesity, Blaser's team fed infant mice low doses of

penicillin to mimic doses given to farm animals. After 30 weeks,

penicillin-fed mice were between 10 and 15 per cent bigger and twice as

fat as drug-free mice.

When the team looked at the mice's gut bacteria, they found that the

antibiotic-fed mice had a different complement of bugs to the untreated

mice. Low doses of antibiotics had seemingly shifted the balance of

certain gut microbes, reducing the numbers of /Lactobacillus..../

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