Weight, adiposity, and physical activity as determinants of an insulin sensitivity index in pima Indian children.
OBJECTIVE
To determine whether measures of physical activity are related to an insulin sensitivity index ([ISI] 10(4)/fasting insulin x glucose) independent of weight or adiposity in children.


METHODS
We conducted a longitudinal study of 90 Pima Indian children (39 boys and 51 girls) at 5 and 10 years of age measuring adiposity (dual-energy X-ray absorptiometry), physical activity behavior (questionnaire: number of activities per week [ACT], average hours per week [TIME]), and energy expenditure (doubly labeled water: physical activity level [PAL]).


RESULTS
In cross-sectional analyses, ACT was correlated with ISI at 5 years of age (r = 0.24, P = 0.02) and at 10 years of age (r = 0.21, P = 0.05), but these relationships were not independent of weight or adiposity. PAL was correlated with ISI at 10 years of age (r = 0.39, P = 0.03) but was not independent of weight or adiposity. Longitudinally, ISI decreased from 5 to 10 years of age, and increases in weight and adiposity were associated with decreases in ISI (r = -0.51 and -0.41, respectively; both P < 0.0001). ACT decreased from 5 to 10 years of age, but children who had smaller decreases in ACT had smaller decreases in ISI, independent of increases in weight or adiposity (partial r = 0.22, P = 0.04 adjusted for either weight or adiposity).


CONCLUSIONS
These data suggest that early establishment and maintenance of an active lifestyle can have a beneficial effect on ISI that is partially independent of changes in weight or adiposity. This is particularly relevant considering the current epidemics of both obesity and type 2 diabetes in children.
Bunt
Joy C
JC
Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Phoenix, Arizona, USA. jbunt@mail.nih.gov
Salbe
Arline D
AD
Harper
Inge T
IT
Hanson
Robert L
RL
Tataranni
P Antonio
PA
D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000033:anatomy & histology*; D001130:Arizona; D001823:Body Composition; D001824:Body Constitution; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007198:Indians, North American; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D000078790:Insulin Secretion; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology*; D012044:Regression Analysis; D012727:Sex Characteristics
D007328:Insulin