Researchers say your genes can determine where you store belly fat, and that can have health consequences.
Genetics can make everything from brown hair to chronic disease more likely.
Now, having an “apple-shaped” or “pear-shaped” body can be added to that list.
That discovery could open the door to new treatments that might target those variants in order to help prevent obesity.
The waist-to-hip ratio — the circumference of the narrowest part of the waist divided by that of the widest part of the hips — can be an indicator of increased risk of heart disease, diabetes, and high blood pressure.
More fat around the waist relative to the hips results in a higher ratio and increased risk.
That’s in part because belly fat sits around vital organs such as the kidneys and heart, said Ruth Loos, PhD, director of the Genetics of Obesity and Related Metabolic Traits Program at the Charles R. Bronfman Institute for Personalized Medicine, part of the Icahn School of Medicine at Mount Sinai in New York, and one of the authors of the new study.
That fat, Loos told Healthline, “is more likely to interfere with organ function, whereas if you store it on the hip or thighs, it’s more safe there.”
She and her colleagues wanted to know more about the biology behind that fat distribution.
“If we know what biology links it, maybe we can unlink it,” she said.
Loos and her team looked at the genetic variations of more than 476,000 individuals in more than 70 different geographic locations.
They then compared the variations to the subjects’ waist-to-hip ratios, focusing on nearly 230,000 variants they had predicted might play a role.
Of those, they found 24 variants that predispose people to a higher waist-to-hip ratio, 9 of which are relatively rare and 15 of which are common.
The researchers also found those variants work to influence fat storage by affecting metabolism, fat tissue, bone growth, and a hormone that breaks down fat.
There is still a lot of work to be done, Loos said, but the research raises the possibility of one day seeing a breakthrough such as a drug that would target a particular gene and affect how it works.
How genes influence obesity has been studied for years, primarily in how they might affect body mass index, influence factors like a propensity to overeat, and regulate whether fat is stored or released by certain cells.
One such research effort found a genetic variant that causes energy from food to be stored as fat rather than burned off.
Another identified 25 genetic factors that also affect metabolism and may affect how it influences weight gain.
A study published in January found a gene predisposes some people to “persistent healthy thinness.”
That’s why a genetic test to see whether you carry a variant tied to increased risk of obesity — or a particular fruit-based distribution of that fat — wouldn’t be particularly helpful, said Loos, who is also a professor at the Icahn School of Medicine.
For one thing, most adults can already look down and tell which variants they likely have. But even for younger people, the information wouldn’t necessarily be all that useful.
“If you see that a newborn baby carries a lot of genes tied to apple shape, you still can’t say for sure that they’ll become apple shape,” Loos said, “because the genes we identified explain only a small part” and leave out the impact of environmental and other factors that can lead to weight gain.
But that works both ways.
Even if you carry genes that predispose you to obesity or an apple-shaped body, a healthy lifestyle can overcome them.
You might have to work harder at it than someone with other genes, but genes just increase the risk. They aren’t destiny.
New research identifies two dozen genetic variations that may increase the likelihood someone is apple-shaped or pear-shaped.
Being apple-shaped — storing excess weight around your belly rather than around your waist — carries more risk for obesity-related disease.
So the research raises the possibility of a treatment that may one day be able to target the genes that increase this risk so it can be mitigated.