Air pollution may contribute to the global obesity epidemic, according to new findings suggesting that babies exposed to diesel exhaust in the womb are significantly more likely to become obese in later life.

A new study on mice, published in The Journal of the Federation of American Societies for Experimental Biology, found that pregnant mice exposed to high levels of air pollution gave birth to offspring with significantly higher rates of obesity and insulin resistance in adulthood compared to offspring that were not exposed to polluted air.

Additionally the effect of air pollution and weight appeared to be especially prevalent in male mice, which were heavier regardless of diet. 

"It is becoming clearer that our environment profoundly affects our health in ways that are little understood," co-researcher Dr. Jessica L. Bolton, from the Department of Psychology and Neuroscience at Duke University in Durham, NC, said in a statement.

"We believe these data have important implications for health disparities as a consequence of socioeconomic conditions, in which low income neighborhoods tend to be disproportionately exposed to high levels of pollution, which we hope will inform policy and regulation decisions," she added.

The study included two groups of pregnant female mice. Researchers exposed one group to diesel exhaust during the second half of pregnancy and the other group to filtered air for the same amount of time.

Researchers kept all the pregnant mice in specialized chambers for four hours each day, breathing either polluted or filtered air, and then returned the mice to their normal housing after the exposures.

Scientists analyzed some of the fetal brains of the mice from both groups by measuring the amount of immune proteins to observe the fetal brain immune response to the in utero pollution exposure.

Once the offspring became adults, researchers placed them on either a low-fat diet, which comprised of 10 percent saturated fat, or a high-fat diet, made up of 45 percent saturated fat, but with all other nutritional aspects being identical.

Researchers measured offspring food intake, body weight and activity levels before putting the mice on their diets, and then every week throughout the period of the study.

Researchers measured metabolic hormones of the mice after six weeks and found that while female mice from diesel-exposed moms never developed insulin resistance and were only heavier than control females if they were fed a high-fat diet in adulthood, males from diesel-exposed moms were heavier than the males from clean air-exposed moms regardless of their diet as adults.

"If you're pregnant and have a long drive into work, you might think twice about opening the car windows," Dr. Gerald Weissmann, Editor-in-Chief of the FASEB Journal said in a news release. "It's already been established that risk factors for obesity (junk food, high fat-high cholesterol diets, etc.) begin as early as the womb. This important study shows that the air a mother breathes is also one of those risk factors."