What Is Your Weight Destiny?

Your Genes and Obesity

Oh, please. Just shut up, already.

That's what I have begun to tell myself whenever I catch my mind noodling around with the same thought I've had a half dozen times a day for my entire adult life: I wish I could lose a few pounds.

You see, I'm not fat and have never been more than a little overweight -- the freshman 15, too much edible merriment around the holidays, that kind of thing. I'm one of those women, quite possibly like you, who worry when they've put on a couple of pounds, but who usually look perfectly fine -- great, even, on a good day, depending on the spandex content of their jeans -- and who stay within a healthy weight range. Yes, I exercise a lot and try to eat right, but I'm also lucky -- damn lucky. Exactly how lucky, I didn't realize until I reported this story.

The question was, are there some of us who, despite doing almost everything right, are destined to be fat, thanks to our genetic makeup, outside factors that make it tougher to exercise and eat right, or some evil fat-bestowing fairy visiting us while we sleep? Are we going to end up being one of the 34 percent of Americans who are overweight or the 34 percent who are obese, according to the Centers for Disease Control and Prevention, no matter how hard we try?

Turns out, the answer is no, but yo-yoers beware: There is mounting scientific evidence of a tipping point of pudginess after which losing the weight you've gained -- and keeping it off -- gets a heck of a lot more difficult.

While hundreds of genes affect weight in small ways, several known mutations run in families and clearly appear to predispose those who have them to obesity. (These mutations are not routinely screened for, so don't expect your doctor to uncover them in your annual blood tests.) That said, how your genes express themselves may be largely up to you. "The genetics of obesity is not well understood," says Howard Eisenson, MD, the executive director of the Duke Diet & Fitness Center. He points out that research suggests that genetics accounts for 50 to 70 percent of our weight variability, meaning that being fat, even if you're loaded up with the "bad" genes, is in no way a done deal. "Just because someone has a lot of obesity in her family doesn't mean she will inevitably develop it," Dr. Eisenson says.

Yes, someone who is genetically predisposed to gain­ing weight is going to have a harder time controlling her hunger when she's plunked down in the cookie aisle -- some of the genetic mutations involve a resistance to the hunger-suppressing hormone leptin -- and a harder time losing weight once it's gained than someone without that genetic makeup. Amy Young,* 33, of Silver Spring, Maryland, has never been tested for an obesity gene, but she may well have one. She grew up with both parents and her two sisters being overweight (although her brother was not). "I would read about dieters who would say, 'I just stopped eating six milkshakes and fried chicken, and I lost all this weight,'" says Young, whose highest weight at five foot five was 280 pounds. "I never did that. I never ate anything fried, and we never had junk food or bags of chips or Oreos." Nonetheless, she and one of her sisters were heavy from childhood. At a weight-loss camp, they shed a considerable number of pounds but promptly packed them back on. "That regain was more traumatizing than being heavy in the first place," Young says. She has since been a patient of Dr. Eisenson's, and while thinner now, she works hard to keep her weight below 200 pounds. She tracks her food, eats 1,800 calories a day (she's a nursing mom), and does a daily hour of cardio as well as working out with a trainer two to three times a week. "I can't do any more," she says.

Young's story stands in stark contrast to Samantha Murphy's. Murphy, who is 30 and also five foot five, weighs about half as much: 104 pounds. She has always been thin, as has her entire family. "I try to have a lot of fruits and vegetables, but I basically eat what I want when I want, sometimes healthy, sometimes not," says Murphy, who lives in Greenwich, Connecticut. She exercises only once a week (although she walks three miles to work) and is a professed chocolate lover who eats it "at least once a day." That's not to say Murphy overeats; to maintain a weight of 104 pounds with little exercise requires eating approximately 1,456 calories a day. She says she gets full quickly and listens to her body's signals to stop eating, perhaps a sign that the hormones that regulate satiety are working well. "It's just the way I am."

Being thin may not come as easily or as naturally to most of us, but even among people who have a genetic tendency toward obesity, there are those who never get fat. "There are lots of different behavioral strategies to losing weight and keeping it off," Dr. Eisenson says. Some of his patients count calories religiously, others cut carbs or fats, some cannot indulge at all, and still others find that the occasional treat prevents splurges. "None of these works for everyone," Dr. Eisenson says. "You have to take a good, hard look at what you're willing to change for good."

*Name has been changed for privacy