--- title: Antibiotics and Weight: Overprescribing Can Lead to Obesity description: A new study finds the strongest evidence yet that antibiotics in early childhood can contribute to more, and lasting, weight gain canonical: https://time.com/4082242/antibiotics-obesity/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2015-10-21T20:08:39.000Z article:modified_time: 2026-08-04T07:57:23.551Z article:section: Health og:title: Too Many Antibiotics May Make Children Heavier og:description: A new study finds the strongest evidence yet that antibiotics in early childhood can contribute to more, and lasting, weight gain og:url: https://time.com/4082242/antibiotics-obesity/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=1000&quality=75&auto=webp&crop=16:9 og:image:width: 1000 og:image:height: 563 og:image:alt: TIME.com stock health rx prescription bottle drugs og:type: article twitter:card: summary_large_image twitter:title: Too Many Antibiotics May Make Children Heavier twitter:description: A new study finds the strongest evidence yet that antibiotics in early childhood can contribute to more, and lasting, weight gain twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=1000&quality=75&auto=webp&crop=16:9 ---  # Too Many Antibiotics May Make Children Heavier > Sponsored content. 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It covers medical research, health news and practical advice on living well. #### Where can I get reliable health news by email? Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ## Video: Science Cop: How Anti-Vaxxers Put Everyone at Risk [Watch (HLS stream): Science Cop: How Anti-Vaxxers Put Everyone at Risk](https://cdn.jwplayer.com/manifests/ai82XWJ8.m3u8) (2:06)  _Published 2014-09-24. TIME's Science Cop Jeffrey Kulger takes on the misinformation coming from opponents of childhood vaccinations_  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Oct 21, 2015 8:08 PM UTC  Illustration by Sydney Rae Hass for TIME  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Oct 21, 2015 8:08 PM UTC There’s growing evidence of the long-term health problems linked to too much exposure to antibiotics. Not only are the drugs becoming less effective as bacteria become resistant to existing medicines, but they are changing our bodies, particular those of young children, in potentially unhealthy ways. In the largest and longest study so far looking at how antibiotic exposure affects body mass index (BMI), researchers found that the more doses and the longer children are exposed to antibiotics, the more likely they are to retain weight gained and to gain more weight over time. **MORE:** [Antibiotics Are Linked To Type-2 Diabetes](http://time.com/4013398/antibiotics-diabetes/) Led by Brian Schwartz, professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health, the team looked at electronic health records of 142,824 children between the ages of three and 18 years. They broke down antibiotic prescriptions by what effect they had on BMI—whether it was temporary, or reversible and the weight that was gained associated with the drugs was lost within a year, or whether the effects were more long lasting, and the weight didn’t come off. Reporting in the [_International Journal of Obesity_](http://www.nature.com/ijo/index.html), they found that having any antibiotic prescription in the past year (most received two prescriptions on average) before children’s BMI was measured resulted in a weight gain, but that this weight was lost soon after the medication was stopped. When the researchers looked at the cumulative effects of the drugs, however, they found that compared to children who did not take any antibiotics, those who did were more likely to gain and hold onto weight, and eventually even gain more weight by the time they were 18 years old. **MORE:** [There’s Yet Another Downside To Overusing Antibiotics](http://time.com/3967873/antibiotic-resistant-bugs/) “The more antibiotics you get, the stronger the effect,” says Schwartz. “And this effect seems to get larger as you get older.” Overall, using antibiotics contributed to anywhere from 1.6 pounds to 3.3 pounds of weight gain during childhood. Schwartz says that the drugs are likely having this lasting effect on weight through the microbiome, or the population of bacteria living in the gut. There is growing evidence that changing the makeup of these “good” bacteria, which help to digest food and maintain the health of the immune system and intestinal tract, may affect things like body weight. Antibiotics may wipe out existing microbiomes and replace them with other, less beneficial bugs, and that may adversely affect weight. The fact that prolonged and continued exposure to antibiotics results in additional weight gain seems to support this theory. “A single antibiotic can wipe out an entire intestinal microbiome,” says Schwartz. “If antibiotics are infrequent, then the microbiome can recover. But if there are excessive antibiotics, then the impacts on the microbiome can last, and the ecology of the bacteria in the intestinal tract changes and doesn’t go back to what it was before.” **MORE:** [This Chart Shows How Hard It Is to End Childhood Obesity](http://time.com/3700930/childhood-obesity-michelle-obama-lets-move/) While his team accounted for other factors that could affect children’s weight, they could not factor in the potential influence of the children’s mother’s microbiome during pregnancy. Some evidence suggests that babies born via Cesarean section, and therefore not exposed to the mother’s vaginal microbes, tend to be heavier and more susceptible to certain immune conditions such as allergies and asthma. The results, says Schwartz, stress the need to use antibiotics sparingly and only when absolutely necessary. Not doing so could continue to put more children at risk of obesity, even if they’re eating right and exercising. ## Transcript So, our recent report claimed that a 2004 study withheld a link between vaccines and autism in African American boys. No surprise, the anti- vaccine crowd considered this a big win. But again and always, they're wrong. Here's why. [ MUSIC ] First, the subjects excluded from the study had no birth certificates available. Meaning data on their mother's age, race and more could not be confirmed. And that information was vital for the work the investigators were doing, More important, the people criticizing the research make the familiar mistake of confusing associated with causation. While it's true that the study did find a slightly higher rate of autism among some kids vaccinated between 24 and 36 months of age, it's almost certain that those children were already autistic and were vaccinated later as part of a basic health requirement for attending special education program [ MUSIC ] programs. If you join the Army and get a mandatory crewcut before basic training, you don't then conclude that military service causes baldness. Finally, the narrator of a disgraceful web video spreading the rumors about the study is Andrew Wakefield. The British researcher whose fraudulent 1998 paper falsely linking vaccines to autism got the entire got the entire anti- vaccine mess started. Wakefield has had his license to practice medicine revoked in the UK. And is hardly in a position to be offering opinions on anything at all. So for the billionth time, vaccines are safe, effective and vitally important. Rumor mongering, on the other hand, can kill. 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