Are chubby children destined to become fat teenagers who grow up to be obese adults?
Research suggests that the problem of childhood obesity, which has escalated alarmingly in the last two decades, reflects a complicated and still poorly understood mix of genetic and environmental factors. Weight-control experts say that while fatness in infancy does not predict excess fat later in life, overweight at later stages of childhood becomes an increasingly accurate predictor.
"All the data does suggest that obesity tracks across age groups," says Leonard H. Epstein, a pediatric obesity researcher who is professor of psychology at the State University of New York at Buffalo. "The important factors are the age of the child and the degree of obesity in the child and in other family members."
Studies have found that 40% of fat 7-year-olds will grow up to be overweight adults, while 70% of overweight children 10 to 13 will become fat adults. Numerous researchers have found that obesity runs in families: A child with two fat parents has an 80% chance of being fat as an adult; the risk is cut in half if only one parent is obese. By contrast a child of two normal-weight parents has a 14% chance of growing up to be fat.
While the findings of population studies indicate that the tendency toward obesity is inherited, environmental factors--such as the time spent watching television, parental feeding styles and attitudes toward weight--play a critical and possibly decisive role.
Increasingly, researchers are studying parental feeding behaviors and their relationship to obesity in children and adolescents. "There's ample evidence that fatness is genetic," says Ellyn Satter, a Madison, Wis., family therapist and dietitian who has written several books about children and food. "But many times parents and others interfere with a child's normal regulatory processes and make the child fatter than he or she otherwise might be."
Interference, Satter says, can be subtle or overt and is not confined to the families of overweight kids. Traditional child-rearing practices can fuel future weight problems. Such practices include forcing children to "clean their plates"; bribing them with food; using dessert as a reward rather than making it a normal part of a meal; forbidding children to eat foods such as candy or cookies because they're too fattening or harmful; and discussing how much or how little children eat in their presence. Most experts warn that placing children on restrictive, low-calorie diets without a compelling medical reason and a doctor's supervision is particularly harmful because it can permanently stunt growth.
"Infants are born with the ability to regulate their caloric intake," says Joanne Ikeda, a dietitian at UC Berkeley who treats overweight children.
She cites studies that demonstrated that babies fed concentrated formula drank less, while those given diluted formula consumed more to compensate. "This ability to regulate intake extends to the preschool years and varies tremendously from meal to meal," she says. "Where and how kids lose this and start responding to external cues, we don't know."
The loss of that ability may mark the beginning of a pattern of overeating that can last a lifetime.
"It's a very interesting area," Epstein says. "You have to figure that if young kids can regulate their eating and adults can't--and adults are notoriously poor at it--something has happened along the way."
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Obesity Study Still Holds Up
One of the most often cited studies on the genetics of obesity was published in 1986 in the New England Journal of Medicine.
Researchers led by Albert J. Stunkard of the University of Pennsylvania studied 540 Danish adults, nearly all of whom were adopted before age 1. Stunkard divided the adoptees into four groups: thin, median weight, overweight and obese. He compared their height and weight with those of their adoptive parents and their biological parents. He found no correlation between the weights of the adoptees and the parents who raised them. There was, however, a strong relationship between the adoptees and their biological parents.