Antibiotic Use and Obesity—Is There a Link?

With Alison Tribble, MD, Guillermo Perez Perez, MD, and J. Michael Gonzalez-Campoy, MD, PhD

There are good reasons to take an antibiotic: bronchitis, sinus infections, and ear infections. Yet, repeated exposure to antibiotics can lead to antibiotic resistance,1  which you no doubt already know.

There may be another reason for concern, especially during pregnancy and in infancy. New research suggests that babies who experience repeated exposure to antibiotics may be at increased risk of excess weight gain during childhood and even later in life.2,3

Excessive exposure to antibiotics may increase the risk of future obesity.While weight gain occurs for many reasons, repeated use of antibiotics may be a possible contributing factor, suggesting another reason to avoid taking (or giving to your child) except when absolutely necessary. Photo: FatCamera @ iStock

Could Reliance on Antibiotics Be Contributing to Obesity?

Findings from several recently published studies may help inform you about this ongoing debate.

In the first study, a team of researchers in New Zealand examined the medical records of more than 132,000 mothers and more than 151,000 children, from 2008-2011, to record the frequency of their antibiotic use during pregnancy and/or in early childhood (up to age 2 years). Then, they looked to see which children experienced obesity at age 4 years.2

Here’s what they found—Among women taking antibiotics during pregnancy as well as when these babies received antibiotics during early childhood, there was a noticeable linked with an increased chance of obesity at age 4 years in those with the greatest exposure.2

Yet, when the researchers analyzed siblings compared to twins, this same pattern wasn’t as clear, leading the researchers to conclude that ''antibiotics are unlikely to be a major contributor to childhood obesity."2

Not so fast, according to the researchers of a second study, also conducted in New Zealand, looking at a possible relationship between antibiotic use and weight gain.3 These researchers report that the children who were exposed to antibiotics during their first year of life had a slightly higher BMI-for-age  score than did those who were not treated with any antibiotics until after their first year of life.

In yet another study, led by Alison Tribble, MD,  a pediatric infectious disease specialist and an assistant professor of pediatrics at the University of Michigan in Ann Arbor, the focus was to look at antibiotic prescribing in hospitals.

Her team evaluated the records of nearly 12,000 young patients, who came from 32 different children's hospitals across the United States.

Here, the researchers determined that t about 1 in 3 children who were admitted to the hospital were given an antibiotic, and about 25% of them were not getting the appropriate treatment, meaning they were given medicine for the condition being treated, or they received the wrong dose.4

Should We Take the Antibiotic (or Give It to Our Kids) or Not?

Even though the findings from all three studies don't align, the experts who issued an editorial discussing this conundrum look at it this way—what we know about the potential role of antibiotics affecting body weight is as follows: "while neither necessary nor sufficient as a cause" of childhood obesity, the frequency of antibiotic use cannot be ignored.5

They add that because antibiotics appear to produce changes in the bacterial make-up of the stomach (also known as the gut microbiome), which has been positively linked with weight gain and metabolism, the issue of antibiotics is important to consider. However, many questions about if and how antibiotics may influence weight gain still remain.

Dr. Azad and Dr. Owara, in writing their editorial, wonder whether the use of antibiotics is a direct cause of obesity at least in some people and if there might be a specific timing (age, compromised health) or type of antibiotic medication that may be more responsible for promoting this adverse effect.5

The Cause of Overweight and Obesity is Multifactorial

The experts stress the importance of recognizing that our bodies are influenced by many environmental considerations, just as our gut bacteria are affected by many factors in addition to our genetics, so there is not one single cause or reason that obesity may arise.

"Antibiotics alone are not responsible for the current outbreak of obesity," Guillermo I. Perez Perez, MD, a research associate professor at New York University Langone Medical Center, tells EndocrineWeb.

"I feel that the current knowledge is still unclear related to the use of antibiotics [and any related obesity risk]," says Dr. Perez Perez.

Dr. Tribble agrees but with a voice of caution: "It does seem plausible" that frequent or repeated antibiotic use might increase the potential for developing obesity, she says. "But the actual link is still a little murky” but it’s fair to say that “It's a fairly modest effect with each dose of antibiotic—if there is one."

For people who must seek treatment in a hospital, the research points to the need to be sure that your healthcare team is following what is known as an antibiotic stewardship program, which are national guidelines that govern best prescribing practices for antibiotic use in medical faciltities.6

As is often the case, the research, has produced mixed and somewhat conflicting findings.2,3 "Some [studies] have shown a clear link, others a questionable [one],'' says Dr. Tribble.

Despite the lack of a consensus on whether taking antibiotics may influence future weight status, these studies are still valuable, says J. Michael Gonzalez-Campoy, MD, PhD, FACE, medical director and chief executive officer of the Minnesota Center for Obesity, Metabolism, and Endocrinology, in Eagan, Minnesota. He reviewed recent studies for EndocrineWeb as he was not involved in the research.

These new trials are of benefit, he said, because they ''add to our current understanding of the complexity of obesity as a chronic disease that is genetically-based but influenced by the environment."

Parents, in particular, might benefit from learning more about what we now know about the link between antibiotic exposure and obesity and to heeding the experts' advice on what to ask your healthcare providers when considering the need for an antibiotic.

It's also fair to say that paying attention to food choices and encouraging daily activity are even more important when raising concerns about future overweight.

Advice While Pregnant and for Parents of Young Children

While some researchers believe we should act based on the possibility of a link between antibiotics and obesity, Dr. Tribble says it would be the wrong to suggest that they should avoid antibiotics for themselves and their babies out of concerns about it leading to overweight.

Antibiotics are often necessary, and needed for only five to 10 days, short course to successfully treat a bacterial infection.

However, for now, Dr. Perez Perez said, the research is ''another reason to avoid antibiotics for children unless they are critical." And, he reminds parents, don't overlook the importance of a healthy diet and daily exercise to keep children's weight at a healthy level. 

Meanwhile, if your child's doctor prescribes an antibiotic, Dr. Tribble suggested asking a series of questions:

  • Is the antibiotic or antibiotics necessary?
  • Why is it or they being used?
  • How do you know this is the right antibiotic for this illness (ie, correct frequency, dose)?

Despite programs set up to monitor hospital antibiotic use, over-prescribing still occurs, Dr. Tribble said. And, overuse also occurs even more often at the doctor’s office. Have you ever called your doctor because you’re suffering from a cold that won’t quit or horrible pressure in your sinuses to insist your need an antibiotic? Or, called the pediatrician to say your child can’t sleep because he has had an earache for days?

Instead, it’s important to ask enough questions when told you need an antibiotic.  That way, when the doctor writes a prescription “because your kid really needs the antibiotic, it's okay," Dr. Tribble says. But she emphasizes the need to raise concerns about whether an antibiotic is essential or if there are any other options to consider. 

As for parents of older children who may be struggling with their weight and worry about having given their children antibiotics. "I don't think a parent should feel guilty," says Dr. Tribble. We learn as we go.

Advice on Antibiotic Use from the CDC

Experts from the federal Centers for Disease Control and Prevention (CDC) urge you to ''Be antibiotics aware."

By that, they mean to use antibiotics appropriately and smartly. 

While prescriptions for an antibiotic are dispensed as needed on an individual basis, the CDC  lists common conditions that respond to this treatment: when the common cause is a bacterial (which antibiotics can help) or viruses (for which antibiotics don’t work).

Common illnesses that are caused by bacteria include: strep throat, whopping cough and urinary tract infections, while the common cold, a sore throat, and the flu are typically caused by a virus in which case, the best treatment is time, to let your system fight the virus and eventually beat it.

There are, of course, some ''gray" areas. Sometimes, the illness may begin with a virus and then because you are susceptible you get a bacterial infection, too. For instance, a sinus infection could be caused by bacteria or virus, as can a middle ear infection, so the CDC says these conditions are considered ''maybe" for antibiotics with these kinds of diagnoses.

There’s one exception—Bronchitis, which may be caused by bacteria or a virus, the CDC recommends avoiding use of an antibiotic to treat this illness,1 noting that "studies show that in otherwise healthy children and adults, antibiotics for bronchitis won't help you feel better."

What Can You Do for Children with Obesity?

In a review of randomized trials of individiuals who were less than 19 years of age across 38 studies, the pooled results suggest that metformin offers an effective treatment in children who are already following a healthy lifestyle.7  The findings appear in the peer-reviewed journal, Childhood Obesity.

Metformin is the most commonly prescribed medication used to manage blood glucose in individuals diagnosed with type 2 diabetes as well as in children with obesity who have type 1 diabetes.

The cummulative results offer sufficient evidence that children who received metformin experienced a signficiant reduction in a variety of fat mass indices, including: body weight, waist circumferance, body mass index, and overall fat mass.7  

If you have a child with overweight or obesity, it may worthwhile to discuss all the actions you might take to help your child achieve meaningful weight loss in a healthy manner. For some, you and your child's pediatrician may want to onsider adding metformin to assist in effective weight loss.

None of the doctors have any financial conflicts with regard to reported studies.

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