For over 50 years, the agricultural industry has used subtherapeutic antibiotic therapy, or STAT, to promote weight gain in livestock that are being raised for their meat. These antibiotics are not administered to fight infection or disease, but rather to induce rapid weight gain that would not occur naturally. Low dose antibiotics have enjoyed a reputation as growth promoters for decades, but theories regarding exactly how antibiotics promote weight gain remained unproven until August 22, 2012, when the NYU study was published online in Nature.
The hypothesis was that low doses of antibiotics can affect the function and composition of the microbiome (bacteria community) inside the stomach. Stomach bacteria help digestion and nutrient absorption by metabolizing nutrients as food gets broken down inside the stomach. When these bacteria are manipulated or otherwise disturbed, the manner in which your body processes and metabolizes food changes significantly.
Researchers at NYU administered STAT to a group of normal mice and observed that, in comparison to the control group, the mice that had received antibiotics developed nearly 10-15% more fat mass after roughly six weeks, along with increased percent body fat. Researchers observed higher bone density in mice who were given STAT early on in their development, and also noted that hormones related to the mice’s metabolism were altered if the mice received STAT at a young age. Researchers concluded that the exposure to antibiotics altered the stomach microbiome and changed how stomach bacteria metabolize certain nutrients, thus promoting increases in weight and body fat. Although mice were used in this particular experiment, researchers noted in the abstract of their published journal article that “antimicrobial agents of different classes and varying activity are effective across several vertebrate species,” which likely makes these findings applicable to humans and other animals as well.
Dr. Cho, associate program director for the Division of Gastroenterology at NYU School of Medicine, notes that the scientific community is far from fully understanding the stomach microbiome and how it affects body composition, general health and disease. However, as we collect more information on the microbiome and its interactions, this recent finding regarding the relationship between antibiotics and weight gain could be very significant, revealing a lot about a variety of conditions including adult metabolic syndrome and childhood obesity.
Antibiotic use has increased significantly in recent years, with American children receiving approximately one antibiotic course annually. With the increase in antibiotic use, concerns have risen regarding some of the long-term effects of frequent administration of antibiotics. Many doctors have stopped recommending antibiotic treatment to cure certain infections, stating that excessive medicine can actually weaken the immune system over time by not allowing the body to fight off infections naturally, and also by killing off only the weakest bacteria while allowing antibiotic-resistant bacteria to survive and reproduce.
With the presentation of NYU’s study on antibiotics and metabolism, we may have something else to worry about regarding antibiotic treatment and healthy childhood development. Lead researcher Martin J. Blaser, chair of the Department of Medicine at NYU Langone Medical Center, explained that antibiotics could play a role in rising obesity rates, saying, “The rise of obesity around the world is coincident with widespread antibiotic use, and our studies provide an experimental linkage. It is possible that early exposure to antibiotics primes children for obesity later in life.”
Obesity is one of America’s most widespread health epidemics, affecting over 1/3 of the nation’s adult population. From the 1960’s to 2005, the percentage of adults in the United States that are obese rose from roughly 13% to 35%. The rate of childhood obesity is approximately 17% of all children in the United States, and many of them will grow up to become obese or overweight adults. We already know that obesity is a direct result of an energy imbalance (taking in lots of calories while not burning enough calories to offset extra intake), but new information on the relationship between antibiotics and our metabolisms could spur more research into how our lifestyles can not only affect what and how we eat, but also how our bodies process and digest the calories we consume. So for now, parents take note. Your child certainly won’t have any fun with that fever or ear infection, but don’t reach for the penicillin just yet. In the long run, he may be healthier, happier, and fitter without it.
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