Two weeks ago scientists announced that a human fat gene, discovered last December, does not communicate to the brain that the body has eaten enough. A second team of researchers reported the discovery of a previously undetected gene in mice that causes fatness by slowing energy metabolism, causing weight gain without large increases in food consumption.

While the precise implications of these discoveries are uncertain, research suggests that the problem of childhood obesity, which has escalated alarmingly in the past 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, said 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.

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Studies have found that 40 percent of fat 7-year-olds will grow up to be overweight adults, while 70 percent of overweight children between the ages of 10 and 13 will become fat adults. Numerous researchers have found that obesity runs in families:A child with two fat parents has an 80 percent 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 percent chance of growing up to be fat.

The discovery of the obesity genes adds to the findings of population studies that the tendency toward obesity is inherited. Even so, environmental factorssuch 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, said 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.