According to a new study, childhood obesity isn't just a result of unhealthy food habits but also the use of antibiotics at a very young age.

The study was based on more than 11,532 children born between 1991 and 1992. Researchers found that children exposed to antibiotics before turning 5 months were 22 percent more likely to be overweight at around 38 months than children who weren’t exposed.

"We typically consider obesity an epidemic grounded in unhealthy diet and exercise, yet increasingly studies suggest it's more complicated. Microbes in our intestines may play critical roles in how we absorb calories, and exposure to antibiotics, especially early in life, may kill off healthy bacteria that influence how we absorb nutrients into our bodies, and would otherwise keep us lean," said Leonardo Trasande, MD, associate professor of pediatrics and environmental medicine from NYU School of Medicine and lead researcher of the study.

For the study, researchers examined medical data of all participating children at different time periods of their development, from birth to 5 months, 6 months to 14 months and 15 to 23 months. Researchers also assessed body mass when each child was six weeks, 10 months, 20 months, 38 months and seven years of age.

Researchers found that children exposed to antibiotics at 5 months and 23 months had a higher chance of being overweight for their age and gender. By the age seven, there was no increased risk for children being overweight or obese.

Researchers have warned that they have shown a correlation between antibiotic use and weight gain and not a causal relationship. They say more research is needed to understand the effect of antibiotics on weight gain among children.

"For many years now, farmers have known that antibiotics are great at producing heavier cows for market. While we need more research to confirm our findings, this carefully conducted study suggests that antibiotics influence weight gain in humans, and especially children too," said Jan Blustein, MD, PhD, professor of population health and medicine, one of the study researchers.

The study was published in the International Journal of Obesity.