Purpose. This dissertation sought to examine the relationship between physical activity (PA) and adiposity in overweight Hispanic (Hisp) and African American (AA) adolescents. Three objectives were addressed, each in a separate study, and the three studies comprise this dissertation. The objectives were (1) to cross-sectionally explore ethnic differences in the relationship between PA and body fat distribution among overweight Hisp and AA adolescents; (2) to cross-sectionally examine sex differences in the relationship between PA and body fat in overweight Hisp adolescents; (3) to examine whether short-term increases in physical activity were associated with improvements in body composition in overweight Hisp adolescents.
Methods. The participants were overweight (BMI > 85 th percentile) Hisp and AA adolescents, grades 9–12, who were participating in one of three obesity intervention studies. Accelerometry was used to assess total PA and percent time spent in MVPA and sedentary. Energy intake was assessed by 3-day diet records. Fat and lean mass were assessed by DEXA, and fat stores, including SAAT, VAT, and HFF, were assessed by MRI.
Results. In study 1, ethnic-specific relationships between PA and adiposity were observed. Higher PA of 100 cpm, or roughly 30%, was associated with 22% lower HFF in AA, but not Hisp. Higher PA was associated with 9% lower SAAT in Hisp, but not AA. In study 2, which only included overweight Hisp adolescents, higher total PA was associated with 9.2% lower SAAT. No sex differences in the association between PA and adiposity were observed. In study 3, which also only included overweight Hisp adolescents, a 30% increase in total PA was associated with a decrease of 1.4 kg in total fat mass and 1% body fat in overweight Hisp adolescents after accounting for the influence of energy intake.
Conclusions. Total PA may be sufficient to improve body composition in overweight Hisp and AA adolescents. Ethnic-specific associations between PA and adipose depots suggest that physical activity interventions may improve body composition differently in Hisp and AA adolescents.
|Commitee:||Berhane, Kiros, Clark, Florance, Davis, Jaimie, Spruijt-Metz, Donna|
|School:||University of Southern California|
|Department:||Preventive Medicine (Health Behavior Research)|
|School Location:||United States -- California|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Subjects:||Black studies, Public health, Hispanic American studies, African American Studies|
|Keywords:||Adolescents, Ethnic differences, Fat mass, Obesity, Physical activity, Sex differences|
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