Female hormone estrogen benefits women but in men, an imbalance of female sex hormones may lead to obesity, especially if you are living in the western developed world.
Obesity among western men could be linked with exposure to substances containing the female sex hormone estrogen - substances that are more often found in soy products and plastic products like PVC.
Hormonally-driven weight gain occurs more significantly in females than in males in the developing world.
"However, in the US, Europe and Australia, the rates of hormonally-driven obesity between men and women are much closer. In some western nations, male obesity is greater than female obesity," explained lead study author James Grantham from University of Adelaide's school of medical sciences.
Exposure to estrogen is known to cause weight gain, primarily through thyroid inhibition and modulation of the hypothalamus.
"Soy products contain xenoestrogens and we are concerned that in societies with a high dietary saturation of soy, this could be working to 'feminise' the males," added Maciej Henneberg, a Wood Jones professor of anthropological and comparative anatomy at University of Adelaide.
This would allow men in those communities to artificially imitate the female pattern of weight gain, he added.
Another well-established source of xenoestrogen is polyvinyl chloride known as PVC.
This product is in prominent use in most wealthy countries - from plastic medical devices to piping for water supplies.
The paper was published in the online journal PLOS ONE.