Repeated Antibiotic Exposure Up to Age 4 Years With BMI at Age 4.5 Years Interview with:
Dr. Carol Chelimo PhD

Research Fellow
Dept. of Paediatrics, School of Medicine
University of Auckland What is the background for this study?

Response: New Zealand has the third highest prevalence of obesity among Organisation for Economic Co-operation and Development countries. Pediatric obesity is associated with development of cardiovascular risk factors in later life, such as type 2 diabetes, hypertension, dyslipidemia, and metabolic syndrome. Antibiotic exposures in early life may affect weight by altering the gut microbiota, potentially increasing the risk of childhood obesity.

The overall aim of this research was to examine whether repeated antibiotic exposure by age 48 months is associated with higher body mass index (BMI) at age 54 months. Specifically, it evaluates whether the number, timing (age), and type of antibiotic exposures are associated with a higher body mass and an increased likelihood of overweight and obesity. This work incorporates antibiotic exposure during pregnancy What are the main findings?

Response: In this research that included 5128 children from the ‘Growing Up in New Zealand’ cohort study, those repeatedly exposed to antibiotics by age 48 months had significantly higher BMI at age 54 months than those not exposed. Compared with no exposure, children with 4 or more antibiotic dispensings had higher adjusted mean BMI-for-age z scores than the unexposed, and receiving more than 9 dispensings was associated with greater likelihood of obesity. In addition, antibiotic exposure in pregnancy was associated with higher BMI in children whose mothers had 2 or more prescriptions; however, antibiotic exposure during pregnancy was not associated with overweight or obesity in these children. What should readers take away from your report?

Response: Antibiotics have many benefits to human health in treating infections caused by bacteria. However, there is concern regarding the over-use or unnecessary use of antibiotics and the potential consequences this.

The association between repeated antibiotic exposure and body mass suggests that repeated antibiotic exposure may be a potentially modifiable risk factor for childhood obesity. Other large cohort studies in Finland, Canada, the United States and the United Kingdom have shown associations that are comparable to our findings. The scientific literature suggests that following antibiotic exposure, many children may not be able to have full recovery of microbiota as the duration required to achieve this exceeds the average interval between antibiotic courses (i.e. additional/repeated exposure).

Antibiotic exposure in animal models also shows comparable effects on weight gain. In addition, there are countries where non-therapeutic antimicrobials are used in livestock feed to accelerate their weight gain; others (e.g. The European Union) have banned the use of antibiotics as growth promoters in animal feed. What recommendations do you have for future research as a result of this work?

Response: This research provides additional evidence, alongside increasing antibiotic resistance, for improved antibiotic stewardship. Future research could examine whether interventions such as antibiotic stewardship programs, which are designed to reduce over-prescribing of antibiotics, also reduce early childhood obesity.

The authors have no conflicts of interest to disclose.


Chelimo C, Camargo CA, Morton SMB, Grant CC. Association of Repeated Antibiotic Exposure Up to Age 4 Years With Body Mass at Age 4.5 Years. JAMA Netw Open. 2020;3(1):e1917577. doi:10.1001/jamanetworkopen.2019.17577


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Last Updated on January 29, 2020 by Marie Benz