The girls' overall level of physical activity was measured for three days with a device that could detect frequency of movement and speed. Their TV viewing hours, height, weight, body-mass index (BMI), percent of body fat and daily calorie intake were also recorded. BMI, a calculation based on height and weight, is a reference used to determine obesity.
At age 12, the activity levels were higher in white girls than in black girls. The black girls had a higher BMI and body fat percentage, and ate more calories daily. They also watched more TV: The median -- meaning half watched more, half watched less -- was 44.3 hours a week for black girls vs. 24.5 for white girls.
Median daily caloric intake was slightly higher for black girls -- 1,912 vs. 1,906 for white girls.
At 12 years of age, 14 percent of the black girls were obese, compared to 4.3 percent of the white girls. At 14 years, 15.6 percent of the black girls and 5.1 percent of the white girls were obese.
That no link was found between physical activity levels and obesity among black girls is consistent with other research showing that fat-burning rates in response to physical activity are lower in black girls during puberty and adulthood than in whites.
Lifestyle issues, rather than genetics, may partly explain the results, said Pete McCall, an exercise physiologist with the American Council on Exercise.
Noting that black girls watch much more TV than white girls, he said, "That would be one area to change." They could shut off the TV and get exercise, "but the neighborhood may not be conducive," he said.
Parent education and income might affect the results, too, McCall speculated. More than half the parents of white girls had a college degree, but fewe
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