While exercise may be beneficial in combating obesity in adolescents, a new study suggests physical activity may be less successful in preventing obesity in African-American girls than in their white counterparts.
The study, published in the Archives of Pediatrics and Adolescent Medicine, examined the levels of physical activity and obesity of 1148 adolescent girls, 538 black and 610 white, between the ages of 12 and 14.
Higher levels of physical activity are prospectively associated with lower levels of obesity in white adolescent girls but not in black adolescent girls. Obesity prevention interventions may need to be adapted to account for the finding that black girls are less sensitive to the effects of physical activity.
The prevalences of overweight and obesity among US youth have increased exponentially since the 1960s,1 - 2 with the largest increases observed in adolescent African American girls.1 Potential contributing factors to the high rates of obesity in African American girls include a higher daily caloric intake,3 more sedentary behaviors (eg, television viewing),4 and lower levels of habitual physical activity5 compared with white girls. Although the roles of factors governing energy balance are well known, evidence suggests that racial/ethnic differences in metabolism at rest6 - 7 and during exercise8 may predispose black girls to becoming obese.
Two laboratory-based studies comparing adolescent girls have shown that black girls have a lower resting metabolic rate,8 - 9 expend less energy during physical activity,8 and, of crucial importance for prevention and treatment, demonstrate lower rates of fat oxidization during physical activity than white girls.