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Are You Destined to Inherit Your Mother's Body Shape?
Mom's overweight and you're hoping not to be? Find out how much control you have over your genes
MARGARET RENKL
Some of Elizabeth's* fondest memories of her teen years are of baking with her mom. They'd stand in the kitchen, aprons tied around their trim waists, licking cookie batter from wooden spoons. "You could be sisters," people would remark, gazing admiringly at their similar slim-but-curvy figures.
Fast-forward a few years, and there's little chance anyone would confuse mother and daughter now. In her late forties, Elizabeth's mom became broader, thicker, and softer, and all traces of the Charlie's Angels-esque proportions of her twenties, thirties, and early forties were erased. And no one was paying closer attention than Elizabeth. "We have the same body type, and I worry that I'll gain weight like she has," says the 22-year-old Chicago artist. "Neither of us ever exercised or watched our diets, but now I've started to do both because I've seen what could be in store for me."
But peeking into your future isn't as simple as taking a look at your mom. Studies suggest that while your genes may determine up to 80 percent of your weight and body shape, environment and personal choice still play a significant role. So even if you're a dead ringer for your mother in old family photos, it doesn't mean you'll enter middle age with the same body. See, she grew up in a world where women never sweat—and never passed up a slice of pie— while you grew up with soccer and diet-meal delivery services, and experts say this distinction can make all the difference. WH dissected the variety of factors that count...and looked at what control you can exert over them.
Body of Evidence
In the 1990s, studies done on identical twins indicated that genes pretty much determined adult shape and size. But new research is uncovering a more nuanced view. Some aspects of shape and size, it turns out, are more closely tied to genes than others. The ease with which you develop muscle mass, for example, is a highly inherited trait. A study that appeared in the International Journal of Obesity found that while you need physical activity in order to build muscle, people who have "muscular" genes require far less exercise than others to look fit. This finding may have surprised certain geneticists—but not 41-year-old Laura. The Nashville state housing director was adopted as an infant and grew up in a sedentary family. Even so, she was always muscular. "When I met my birth mother when I was in my thirties, I saw she had the same lean, fit body. It was like looking into a mirror." Nature, one; nurture, nothing.
The other major finding: Apple-shaped bodies are more genetically linked than pear-shaped or skinny ones. Some speculate this is because you also inherit genes from your father, and men typically store extra pounds in their guts. So if your mother carries weight in her stomach too, it could increase your chances of being an apple. From a medical standpoint, this is worrisome because central abdominal fat is associated with several serious conditions, including type 2 diabetes and coronary artery disease. "You inherit half of your genes from your mother and half from your father, so you're a blend. You can be unlucky and get the worst possible combination from both parents, or be lucky and get the best," says Harvard medical professor C. Ronald Kahn, M.D.
New research has also uncovered a gene that may affect how much you eat. Neurexin 3, one of the genes recently implicated in regulating waist circumference, is also involved in brain function and has been linked to addictive behaviors such as alcoholism. Scientists believe this gene, which is carried by about 20 percent of the human population, may trigger a compulsion to overeat— which could explain why obesity tends to run in families the same way certain body shapes do. "Considering how many factors are involved in obesity, it's interesting that research is increasingly pointing to the brain's involvement in its development," says Kari E. North, Ph.D., an associate professor of epidemiology at the University of North Carolina at Chapel Hill. "Because this gene has been associated with addiction, we need to think about the psychology of weight gain too."
Regrettably, these shape-determining genes can be stubborn. Even disciplined dieters often hit a wall after losing the first few pounds or regain weight they've lost. Researchers believe this is because each person has a baseline weight, a genetically influenced set point where the body naturally wants to be. If you end up more than 10 percent below your set point, your body will fight back. "The more weight you lose, the harder your body works to compensate," says David E. Cummings, M.D., a professor of medicine at the University of Washington. "You become hungrier, and your metabolism becomes more efficient. Increasingly, you begin to crave food—and such a drive is very difficult to resist."
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