Research has identified numerous potential contributors to the obesity epidemic. A lack of diet and exercise and an unhealthy food supply are among those at the top of the list. A new item has been recently added: an alteration in gut flora caused by antibiotic use in infants less than 6 months old.
Antibiotic resistance, superbugs … and obesity?
The consequences of the overuse of antibiotics may include more than antibiotic-resistance and the development of superbugs. Antibiotics could be fattening up people like farm animals by disrupting their gut flora. The idea has been investigated in a pair of recent studies. One study on mice found that antibiotics triggered radical changes in the gut flora that utilize calories and regulate metabolism. The other suggested that children exposed to antibiotics as infants were heavier that their peers.
The human digestive system is a “microbiome,” –a swarm of bacteria, viruses and fungi that break down the complex molecules of food in a form that provides energy to cells. Using antibiotics to fight infection indiscriminately wreaks havoc on the microbiome, killing the good bacteria as well as the bad.
Farmers discovered long ago that the effect of antibiotics on gut bacteria dramatically enhances the growth of livestock. Although the use of antibiotics in animal feed has been practiced for 50 years, no one was sure exactly why they make cattle fatter. But researchers at the New York University Langone School of Medicine believe they have found the answer: changing the microbiome increases the amount of calories harvested from feed.
Antibiotics and the microbiome
Researchers exposed young mice to antibiotics including penicillin, vancomycin and chlortetracycline at levels approved by the USDA for agricultural use. After 7 weeks, the treated mice weighed the same as untreated mice. But instead of tough muscle, they had about three percent more tender body fat.
Certain microbes in the treated mice also underwent genetic changes that made them more active at breaking down complex carbohydrates into short-chain fatty acids—the substances provide energy to intestinal cells and stimulate production of body fat. In other words, the mice were absorbing more calories and packing it on as fat.
A future of microbiome-induced obesity?
Could antibiotics have the same effect on humans? To find out, the NYU researchers analyzed data tracking about 11,500 British children born in 1991-92. They found that infants treated with antibiotics before 6 months of age were 22 percent more likely to be overweight at age 3.
The NYU researchers are moving on to investigate whether the steady trickle of antibiotics from eating meat and dairy products from drug-treated livestock have adverse metabolic effects later in life. They are also looking for clues as to whether the microbiome-induced obesity in humans triggered by antibiotics may accumulate by being passed on to future generations.
That’s a scary thought.