Rethinking Weight
Hey, maybe it's not a weakness. Just maybe. . .it's a disease
Increasingly, researchers are demonstrating that obesity is controlled by a powerful biological system of hormones, proteins, neurotransmitters, and genes that regulate fat storage and body weight and tell the brain when, what, and how much to eat. "This is not debatable," says Louis Aronne, director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital and president-elect of the North American Association for the Study of Obesity. "Once people gain weight, then these biological mechanisms, which we're beginning to understand, develop to prevent people from losing weight. It's not someone fighting `willpower.' The body resists weight loss."
This wonder of natural chemical engineering evolved over centuries to protect humans against famine and assure reproduction of the species. "The idea that nature would leave this system to a matter of `choice' is naive," says Arthur Frank, director of George Washington University's Weight Management Program. "Eating is largely driven by signals from fat tissue, from the gastrointestinal tract, the liver. All those organs are sending information to the brain to eat or not to eat. So, saying to an obese person who wants to lose weight, `All you have to do is eat less,' is like saying to a person suffering from asthma, `All you have to do is breathe better.' "
When Maria Pfisterer looks at her family, she sees her future--and it is frightening. Her father, a diabetic with congestive heart failure and hypertension, weighs nearly 400 pounds, and at age 60 he can scarcely move. Her older sister is also obese and suffers from hypertension. Both Maria and her sister worry they will eventually develop diabetes like their dad.
"My daughter Jordan is very heavy. She's struggling already with weight, and if she gets any more sedentary, I worry what will happen to her," says Pfisterer. "I'm trying to teach her to eat better and keep active. She's into dance, but she'll say, `I'm the fattest kid there.' It breaks my heart."
Pfisterer herself says she does not eat a lot and is always on the go. "I don't eat half gallons of ice cream or bags of chips. But if I lose a little, I regain. I think genetics have a lot to do with it."
Studies of twins. Leibel, director of the division of molecular genetics at Columbia University College of Physicians and Surgeons, has spent a career documenting what Pfisterer knows intuitively. He says, "I believe there are strong genetic factors that determine susceptibility to obesity." Obesity does not result from a single gene, he explains, but rather a variety of genes that interact with environmental influences to increase one's chance of becoming obese. In studies of adult twins, who share many or all of the same genes, BMI, body composition, and other measures of fatness appear to be 20 to 70 percent inherited.
Still, biology is not destiny. Overweight results from one thing: eating more food than one burns in physical activity. Genes simply facilitate becoming fat. "I think the primary problem is on the food intake side," Leibel adds. "There are multiple genes involved in that intake process, and there is good reason to believe that nature and evolution have selected for ingestion of large amounts of food."
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