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Physical Activity, Not Sedentary Time, Predicts Dual-Energy X-ray Absorptiometry–measured Adiposity Age 5 to 19 Years

JANZ, KATHLEEN F.1,2; BOROS, PIROSKA1; LETUCHY, ELENA M.2; KWON, SOYANG3; BURNS, TRUDY L.2,4; LEVY, STEVEN M.2,5

Medicine & Science in Sports & Exercise: October 2017 - Volume 49 - Issue 10 - p 2071–2077
doi: 10.1249/MSS.0000000000001336
Applied Sciences

Purpose To examine the associations among physical activity (PA), sedentary time (SED), and TV viewing (TV) with fat mass (FAT) and visceral adipose tissue mass (VAT) from childhood through adolescence (5–19 yr).

Methods Participants in the Iowa Bone Development Study (n = 230 males and 233 females) were examined at ages 5, 8, 11, 13, 15, 17, and 19 yr. Accelerometers measured moderate- or vigorous-intensity PA (MVPA; min·d−1), light-intensity PA (LPA; min·d−1), and SED (h·d−1). Parent-proxy report (5 and 8 yr) and child-report (11, 13, 15, 17, and 19 yr) measured TV (h·d−1). X-ray absorptiometry scans measured FAT (kg) and VAT (g). Sex-specific growth models were used to create FAT and VAT growth curves for individual participants (level 1), and to test the effect of MVPA, LPA, SED, and TV (level 2) after adjusting for weight, height, linear age, nonlinear age, and maturity.

Results Growth models indicated that low levels of MVPA were associated with high levels of FAT and VAT for males and high levels of FAT for females. TV viewing was positively associated with FAT and VAT for males and females. LPA was positively associated with FAT in males. Sedentary time was not associated with FAT or VAT for males or females (P > 0.05).

Conclusions This study supports current PA guidelines focusing on MVPA rather than SED. The contribution of high TV, but not high SED, to high levels of adiposity suggests that TV’s contribution to obesity is not just a function of low energy expenditure.

1Department of Health and Human Physiology, University of Iowa, Iowa City, IA; 2Department of Epidemiology, University of Iowa, Iowa City, IA; 3Stanley Manne Children’s Research Institute, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL; 4Department of Pediatrics, University of Iowa, Iowa City, IA; and 5Department of Preventive and Community Dentistry, Iowa City, IA

Address for correspondence: Kathleen F Janz, Ed.D., F.A.C.S.M., Department of Health and Human Physiology, University of Iowa, Field House E130, Iowa City, IA 52242; E-mail: kathleen-janz@uiowa.edu.

Submitted for publication February 2017.

Accepted for publication May 2017.

© 2017 American College of Sports Medicine