You know that new car smell?

It could be making you fat — especially if you’re a man in a developed country.

New research from the University of Adelaide suggests that the culprit behind rising levels of male obesity in Western countries could be something other than fat and sugar. The culprit could be the female hormone estrogen.

Overexposure to estrogen may start with what men are eating, especially if their diets are heavy in soy, a component in many food ingredients. Soy products contain plant compounds that mimic the effects of estrogen.

Other items that include estrogen? Any material that contains the kind of plastic called polyvinyl chloride. According to the Center for Health and Environmental Justice, products that contain polyvinyl chloride could range from aprons, bags and backpacks to car dashboards, upholstery and fake Christmas trees. It’s responsible for new car smell, too.

In developing societies, women generally have a higher rate of obesity than men. But these rates have been evening out in Western countries such as the United States, Europe and Australia. In some areas, rates of male obesity even surpass rates of female obesity.

When estrogen makes its way into men’s bodies, it can encourage weight gain by depressing the thyroid and modulating the hypothalamus, the area of the brain that controls hunger. That’s why women usually experience hormone-driven weight gain at a higher rate than men.

The researchers also think there could be a connection between the increased presence of estrogen in men and a reduction in sperm count in Western countries. They say more research is needed to better establish the role estrogen plays in obesity and how products, food and the environment factor into that.

So for now, sniff new cars in moderation.