Study finds antibiotics are unlikely to be a major contributor to childhood obesity
A Better Start National Science Challenge’s research into the association between antibiotic exposure and childhood
obesity is one of the largest studies of its kind ever conducted. It used a sample size of nearly 290,000 children and
their mother’s (151,359 children and 132,852 mothers).
51% of the children were boys. Antibiotics exposure was common, with at least once course dispensed to 35.7% of mothers
during pregnancy and to 82.3% of children in the first two years of life.
The objective of the study was to assess whether antibiotic exposure during pregnancy and/or in early childhood was
associated with the development of childhood obesity.
Obesity is a significant problem in New Zealand and affects 1 in 3 adults and 1 in 9 children. Antibiotics have
historically been used as growth-promoting agents in farm animals and research in animals has shown that use of
antibiotics led to obesity. However, evidence in humans is inconsistent.
Numerous studies have reported a positive association between antibiotic exposure and development of childhood obesity.
However, there are several studies which showed that antibiotics are not associated with the development of childhood
obesity. In these studies, the majority looked at the association between childhood exposure and very few examined
exposure in mothers during pregnancy on obesity.
There is some concern that previous positive studies have not adequately accounted for potential confounding factors
including genetic and environmental factors. In particular, very few studies have studied siblings or twins and the
small studies that did include these analyses reported no associations between antibiotic exposure and the risk of
This study, which has been published in the JAMA Network Open, used national data from New Zealand to assess whether antibiotic exposure in women during pregnancy and/or in their
children early in life was associated with the likelihood of childhood obesity at 4 years of age. In addition, to
address the influence of environmental and genetic factors, the study examined these associations among siblings and
Antibiotics lead to negative changes in the gut microbiome[i]
, which has been proposed to lead to the development of obesity. The mechanisms for this are still unclear but could be
attributed to the ability of gut bacteria to increase energy protection and alter our metabolism and immune function.
However, results from this study indicate there is no association between antibiotic exposure in mothers during
pregnancy and in early childhood on the development of childhood obesity at age 4 years, once the influence of
environmental and genetic factors have been controlled.
“We wanted to better understand the role that antibiotics play in the development of obesity and to investigate for
possible confounding factors that may have influenced these previous results,” says lead researcher, Dr Karen Leong, PhD
candidate and Clinical Research Fellow at the Liggins Institute at the University of Auckland.
There were no associations between prenatal and early childhood antibiotics exposure and the odds of developing
childhood obesity. “While judicious prescription and use of antibiotics is vital, we concluded that antibiotics are
unlikely to be a major contributor to childhood obesity,” says Dr Leong.
“Although antibiotics are not associated with childhood obesity, antibiotics usage in New Zealand is extremely high,
especially during early childhood and it is important to ensure proper antibiotic stewardship among healthcare
professionals and the community at large,” says Professor Wayne Cutfield, Director of A Better Start National Science
A Better Start has supported intervention strategies to combat obesity; specifically the potential role of the gut
microbiome in treating obesity and metabolic diseases, which will soon be published.