The age-old question of why men store fat in their bellies and women store it in their hips may have finally been answered -- it's really all in the genes, says a new study.
"We found that out of about 40,000 mouse genes, only 138 are commonly found in both male and female fat cells. This was completely unexpected.
"We expected the exact opposite -- that 138 would be different and the rest would be the same between the sexes," said lead author Prof Deborah Clegg of the University of Texas wrote in the 'International Journal of Obesity'.
The study involved mice, which distribute their fat in a sexually dimorphic pattern similar to humans.
"Given the difference in gene expression profiles, a female fat tissue won't behave anything like a male fat tissue and vice versa. The notion that fat cells between males and females are alike is inconsistent with our findings," Prof Clegg said.
In humans, men are more likely to carry extra weight around their guts while pre-menopausal women store it in their butts, thighs and hips. The bad news for men is that belly, or visceral, fat has been associated with numerous obesity related diseases including diabetes and heart disease.
Women, on the other hand, are generally protected from these obesity-related disorders until menopause, when their ovarian hormone levels drop and fat storage tends to shift from their rear ends to their waists.
"Although our new findings don't explain why women begin storing fat in their bellies after menopause, the results do bring us a step closer to understanding the mechanisms behind the unwanted shift," Prof Clegg said.