Are Female Hormones Causing Male Obesity?

Women may have more of an effect on men than they thought, or care to admit. An imbalance of female sex hormones among men in Western nations may be contributing to high levels of male obesity, according to new research from the University of Adelaide.

Detailed in the journal PLOS ONE, researchers suggest that obesity among Western men could be linked with exposure to substances containing the female sex hormone estrogen - substances that are more often found in affluent societies, such as soy products and plastics.

The research, led by medical student James Grantham, compared obesity rates among men and women from around the world, using measures such as Gross Domestic Product, to determine the impact of wealth on obesity.

While in the developing world women had significantly greater obesity rates than men, the developed world painted a much different picture.

"Hormonally driven weight gain occurs more significantly in females than in males, and this is very clear when we look at the rates of obesity in the developing world," Grantham said.

"However, in the Western world, such as in the United States, Europe and Australia, the rates of obesity between men and women are much closer. In some Western nations, male obesity is greater than female obesity."

Grantham does not ignore the obvious factor of weight gain in the obesity epidemic, but notes that hormones play a bigger role than previously thought - at least for men.

"Exposure to estrogen is known to cause weight gain, primarily through thyroid inhibition and modulation of the hypothalamus," co-author Professor Maciej Henneberg explained. "Soy products contain xenoestrogens, and we are concerned that in societies with a high dietary saturation of soy, such as the United States, this could be working to 'feminize' the males. This would allow men in those communities to artificially imitate the female pattern of weight gain."

The findings, while astonishing, need further research to better understand whether or not environmental factors are leading to a "feminization" of men in the Western world.