Physical Activity, Fitness and the Energy Cost of Activities: Implications for Obesity in Children and Adolescents in the Tropics - Advances in Food and Nutrition Research - page 83

weekday was strongly associated with overweight/obesity in Vietnamese
adolescents. For children, those who spent 4 h or longer each weekday in
this sedentary activity were four times more likely to be overweight than
those who spent only 1 h or less per weekday. Vicente-Rodr´guez et al.
(2008) also reported that the risk of overweight was increased by 15.8%
per each hour of television viewing. Similarly, Sharifah, Nur Hana,
Ruzita, Roslee, and Reilly (2011) found that the obese children in their
intervention study (MASCOT) spent 89% of their waking day on sedentary
activity and only 1%, or approximately 8 min per day, in moderate to vig-
orous intensity PA. More recently, Al-Nuaim et al. (2012) reported that
larger waist circumference was recorded among adolescents who led a more
sedentary lifestyle.
Nevertheless, there are studies that have reported negative results for the
relationships between PA and obesity. In a case-control study, Amini et al.
(2009) showed no significant difference in daily PA patterns between the
overweight or obese and normal weight groups, suggesting that PA may
not be related to overweight or obese among children. Wang et al. (2006) also
noticed that there were no significant differences in the time spent watching
television and playing electronic games between normal weight and over-
weight adolescents during both weekdays and weekend days.
Based on the available evidence, it is believed that physical inactivity and
sedentary behavior are somehow associated with the development of over-
weight and obesity among children and adolescents. However, the direction
of causality cannot be inferred from cross-sectional associations, as the find-
ings could equally suggest that being obese leads to physical inactivity rather
than the other way around. Recently, a nonintervention prospective cohort
study reported that physical inactivity is the result rather than the cause of
obesity ( Metcalf et al., 2011 ). Nevertheless, there is also evidence that indi-
cates that obesity and physical inactivity are interrelated in a cyclic relation-
ship ( Hallal et al., 2006 ) .
To examine the associations between PA variables and BMI categories
(overweight and nonoverweight), we conducted a logistic regression anal-
ysis using the data extracted from the GSHS. In this analysis, only 20 tropical
countries with complete data for BMI and PA were included and the results
are presented in Table 2.3 . No significant associations were found among all
these countries, except Libya, in which the odds ratio of being overweight
among those participants who did not meet WHO PA recommendations
( WHO, 2010 ) was higher than their counterparts (OR: 1.634; 95% confi-
dence interval: 1.036-2.576).