Belly fat or hip fat - blame your genes

TORONTO - The age-old question of why men store fat in their bellies and women store it in their hips may have finally been answered: genetically speaking, the fat tissue is almost completely different.

“We found that out of about 40,000 mouse genes, only 138 are commonly found in both male and female fat cells,” said Deborah Clegg, assistant professor of internal medicine at University of Texas Southwestern Medical Centre (UTSMC) and senior study author.

“This was completely unexpected. We expected the exact opposite - that 138 would be different and the rest would be the same between the sexes,” Clegg added.

The study involved mice, which distribute their fat in a sexually dimorphic pattern similar to humans.

Sexual dimorphism is the systematic difference between individuals of different sex in the same species.

“Given the difference in gene expression profiles, a female fat tissue won’t behave anything like a male fat tissue and vice versa,” Clegg said. “The notion that fat cells between males and females are alike is inconsistent with our findings.”

In humans, men are more likely to carry extra weight around their guts while pre-menopausal women store it in their 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, said a UTSMC release.

“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,” Clegg said.

These findings appeared in the International Journal of Obesity.