Physical Activity Moving Toward Obesity Solutions: Workshop Summary (2015) / Chapter Skim
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2 Physical Activity and Primary Prevention of Obesity in Youth
2 Physical Activity and Primary Prevention of Obesity in Youth
Pages 27-42
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From page 27... ...
Researchers involved with the Iowa Bone Development Study, a 16-year longitudinal study, found that children and adolescents who are more moderately to vigorously active have lower adiposity. Janz, who was involved in that study, identified it as one of several observational studies on the association between physical activity and adiposity in youth.
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From page 28... ...
EVERYDAY PHYSICAL ACTIVITY AND ITS ROLE IN PREVENTING OBESITY1 Value of Observational Studies for Understanding Physical Activity and Adiposity The two most common study designs used to study healthy children, Kathleen Janz began, are cross-sectional and prospective longitudinal designs. Cross-sectional studies measure the explanatory variable (i.e., physical activity)
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From page 29... ...
One of the useful features of DXA technology, suggested Janz, is that the scanner is backward compatible, so that her research team has been able to rerun old DXA scans and distinguish between visceral and subcutaneous adipose tissue. To provide the workshop audience with a sense of how adiposity changes in children as they age, Janz showed DXA images of two Iowa Bone Development Study participants, a girl and a boy, over a 10-year time span (see Figure 2-1)
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From page 30... ...
Janz cautioned that when one is evaluating the epidemiological literature on physical activity and adiposity, it is important to look carefully to ensure that variation in timing and tempo is being represented. Because the Iowa Bone Development Study data were collected on the same children across time, the investigators have been able to control for individual variation in both timing and tempo, making this a very powerful
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From page 31... ...
The researchers found that total sedentary time does not matter in predicting adiposity, but TV viewing time (a subset of sedentary time) does matter, as does MVPA.
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From page 32... ...
Janz interpreted these results to mean that in general, sedentary time does not appear to be associated with adiposity, but a subset of sedentary time -- probably TV viewing time -- does appear to matter. Janz cautioned, though, that some of the findings related to TV viewing time could be a reflection of researchers having measured this component of sedentary time more than others.
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From page 33... ...
She called for more work in preschool children and possibly prenatally, and she encouraged a greater understanding of the possibility of healthy metabolic profiles in overweight and obese children. Finally, because longitudinal studies are enabling researchers to understand the development of obesogenic behavior in youth, including that some children maintain healthy levels of activity and adiposity through childhood to adulthood, Janz encouraged learning from those families who are "doing it right." PHYSICAL ACTIVITY AND PEDIATRIC OBESITY PREVENTION: PUTTING SCIENCE TO WORK2 The preschool period of growth is unique, Shari Barkin began.
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From page 34... ...
34 PHYSICAL ACTIVITY FIGURE 2-2 Changes in body mass index over time for boys ages 2 to 20 years. SOURCE: Presented by Shari Barkin on April 14, 2015 (Centers for Disease Control and Prevention)
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From page 35... ...
That the children wore the accelerometers for nearly 24 hours per day, compared with the usual minimum wear time of 6 hours, allowed the researchers to asses not only whether the preschoolers were achieving the recommended 60 minutes of daily MVPA but also what that activity looked like. The researchers found that the children spent 14.5 percent of their awake time in MVPA, averaging more than 100 minutes per day, which Barkin said was not surprising.
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From page 36... ...
L Barkin.Figure 2-3 A novel approach to characterize physical activity patterns in preschool-aged children.
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From page 37... ...
Eighty percent of the physical activity involved running games and 20 percent endurance activities. Barkin noted that the segmented nature of the physical activity sessions was consistent with what she and others have learned about how preschoolers move.
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From page 38... ...
Interventions in the Community Setting When Barkin arrived in Nashville, in 2006, the city's then mayor, Bill Purcell, had helped the city double the number of parks and recreation centers, many of them in dense urban areas where residents previously had lacked access to a built environment supportive of physical activity. Barkin and colleagues wanted to take advantage of this "natural experiment" by examining how people were using the newly built parks and recreation centers for physical activity and how use of these facilities could be promoted for routine physical activity in early childhood.
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From page 39... ...
To begin the discussion, Howell Wechsler asked both speakers to identify one public policy change inspired by their research conclusions that they think could have the greatest impact on increasing physical activity in children. Barkin stressed the importance of starting early, given that physical activity patterns are established early.
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From page 40... ...
Barkin observed that the science has focused on MVPA, and much less is known about the health benefits of shifting from sedentary behavior to light physical activity. Based on her observations both in the clinic and in parks and recreation facilities, in her opinion, the latter shift is more achievable than increasing MVPA for many families.
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From page 41... ...
Community Interventions An audience member commented on the association between density of physical activity opportunities in a community and decreased obesity and the importance of educating families about physical activity opportunities. He asked, first, whether a reasonable policy direction would be to increase the density of physical activity opportunities in areas where there is a low density of such opportunities and, second, whether teaching families how to use available facilities could help move them in the right direction along the physical activity gradient.
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