Childhood Obesity and Antibiotics

Much has been written about the relationship between antibiotics and obesity, a subject that is not likely to be exhausted any time soon. Generalizations are difficult because of, once again, multifactorialism. For instance, there are different kinds of antibiotics.

Researchers cannot keep a gang of human subjects under strict control and dose them with different amounts of antibiotics to see what happens; or round up people with infections and divide them into a group that receives antibiotics and another group that doesn’t. That would be profoundly unethical and illegal. They have to depend on records created for other purposes. Those records may not accurate (if, for instance, the patient does not finish all the pills) and are usually not kept with the intention of tracking weight.

Many medical professionals now believe that antibiotics are grossly overprescribed. In addition, the rampant overuse is evident in animal products, which people eat. This is particularly concerning because about 75 percent of the antibiotics fed to animals are not absorbed. According to one estimate, around 22 million pounds of antibiotics are excreted, each year, into wherever factory-farmed animals’ urine and feces end up. Just call it the environment.

An early start

Exposure to antibiotics is common, even before birth. In nations that practice Western medicine, about 80 percent of the drugs prescribed to pregnant women are antibiotics, and about one-third of pregnant women are prescribed at least one systemic antibiotic treatment. Nobody knows how the in utero fetus is affected. Vaginal birth baptizes a baby with microbes on the way out, an experience of which a C-section baby is deprived. Opinion is solidifying into certainty that the omission can have serious consequences.

Because of neonatal sepsis, some newborn babies are treated with IV antibiotics, and there are other reasons for administering them during the first six months. Most probably, antibiotics cause obesity by slaughtering the gut flora. One doctor compared a round of antibiotics to a forest fire. The good bugs die along with the bad bugs, and a healthy population might not be restored for a couple of years, if ever. Many in the medical field now believe that the baby’s microbiome needs to be stocked up with organisms from the mother, to jump-start the establishment of the microbial colonies that will have such a pervasive influence throughout life.

How long has this been going on?

Way back in 1955, the U.S. Navy experimented on a bunch of recruits, and learned that “a 7 week course of antibiotics led to significantly greater weight gain in the treated group compared with placebo.” In 2009, New York University researchers fed low doses of penicillin to lab rodents for 30 weeks, with the result that “penicillin-fed mice were between 10 and 15 per cent bigger and twice as fat as drug-free mice.”

In 2011, Danish scientists hypothesized that “environmental factors influencing the establishment and diversity of the gut microbiota are associated with later risk of overweight.” They reported,

This effect may potentially be explained by an impact on establishment and diversity of the microbiota… Exposure to antibiotics in infancy was found to increase the risk of childhood overweight in offspring of normal-weight mothers, while to some extent reducing the risk of overweight in children of overweight or obese mothers.

(To be continued…)

Your responses and feedback are welcome!

Source: “Antibiotics, infections, and childhood obesity,”, 11/01/16
Source: “Surprise: Antibiotics May Be Contributing to the Obesity Epidemic,”, 04/03/12
Source: “Childhood overweight after establishment of the gut microbiota: the role of delivery mode, pre-pregnancy weight and early administration of antibiotics,”, 03/08/11
Photo credit: Images of Money on Visualhunt/CC BY

Leave a Reply

Your email address will not be published. Required fields are marked *

FAQs and Media Requests: Click here…

Profiles: Kids Struggling with Weight

Profiles: Kids Struggling with Obesity top bottom

The Book

OVERWEIGHT: What Kids Say explores the obesity problem from the often-overlooked perspective of children struggling with being overweight.

About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

Food & Health Resources