Article

Objectively Measured Physical Activity and Fat Mass in a Large Cohort of Children

School of Oral and Dental Sciences, University of Bristol, Bristol, England, United Kingdom
PLoS Medicine (Impact Factor: 14.43). 04/2007; 4(3):e97. DOI: 10.1371/journal.pmed.0040097
Source: PubMed

ABSTRACT

Previous studies have been unable to characterise the association between physical activity and obesity, possibly because most relied on inaccurate measures of physical activity and obesity.
We carried out a cross sectional analysis on 5,500 12-year-old children enrolled in the Avon Longitudinal Study of Parents and Children. Total physical activity and minutes of moderate and vigorous physical activity (MVPA) were measured using the Actigraph accelerometer. Fat mass and obesity (defined as the top decile of fat mass) were measured using the Lunar Prodigy dual x-ray emission absorptiometry scanner. We found strong negative associations between MVPA and fat mass that were unaltered after adjustment for total physical activity. We found a strong negative dose-response association between MVPA and obesity. The odds ratio for obesity in adjusted models between top and the bottom quintiles of minutes of MVPA was 0.03 (95% confidence interval [CI] 0.01-0.13, p-value for trend <0.0001) in boys and 0.36 (95% CI 0.17-0.74, p-value for trend = 0.006) in girls.
We demonstrated a strong graded inverse association between physical activity and obesity that was stronger in boys. Our data suggest that higher intensity physical activity may be more important than total activity.

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    • "In the case of obesity, identifying possible alterations in cost-benefit decision-making is of particular importance. In our obesogenic environment potent food is always available at minimal costs, and excess weight is associated with a reduced motivation for physical activity (Ness et al., 2007) and a possibly heightened valuation of potent food rewards (e.g., Rothemund et al., 2007). Obesity has been characterized by a reduced binding potential of striatal dopamine receptors (Wang et al., 2001; de Weijer et al., 2011). "
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    ABSTRACT: Cost-benefit decision-making entails the process of evaluating potential actions according to the trade-off between the expected benefit (reward) and the anticipated costs (effort). Recent research revealed that dopaminergic transmission within the fronto-striatal circuitry strongly modulates cost-benefit decision-making. Alterations within the dopaminergic fronto-striatal system have been associated with obesity, but little is known about cost-benefit decision-making differences in obese compared with lean individuals. With a newly developed experimental task we investigate obesity-associated alterations in cost-benefit decision-making, utilizing physical effort by handgrip-force exertion and both food and non-food rewards. We relate our behavioral findings to alterations in local grey matter volume assessed by structural MRI. Obese compared with lean subjects were less willing to engage in physical effort in particular for high-caloric sweet snack food. The amount of effort exertion was thereby negatively associated with subjects’ individual levels of chronic stress and punishment sensitivity. Further, self-reported body dissatisfaction negatively correlated with the willingness to invest effort for sweet snacks in obese men. On a structural level, obesity was associated with reductions in grey matter volume in bilateral prefrontal cortex. Nucleus accumbens volume positively correlated with task-induced implicit food craving. Our results challenge the common notion that obese individuals are willing to work harder to obtain high-caloric food and emphasize the need for further exploration of the underlying neural mechanisms regarding cost-benefit decision-making differences in obesity.
    Full-text · Article · Dec 2015 · Frontiers in Behavioral Neuroscience
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    • "Young people who are physically active are less likely to be overweight, have an improved body composition and more favourable cardiovascular risk profile than their less active peers (Janssen and LeBlanc, 2010; Ness et al., 2007). However, few young people are sufficiently active to achieve these health benefits. "
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    ABSTRACT: Background: To examine the tracking of active travel through adolescence, and its association with body mass index (BMI) and fat mass at age 17 in a UK cohort. Methods: We analysed data collected from the Avon Longitudinal Study of Parents and Children (ALSPAC). The analyses include all participants with self-reported travel mode to school at ages 12, 14 and 16 years, and measured height, weight and body composition at age 17 (n=2,026). Tracking coefficients were calculated for individual travel behaviours (including walking and cycling) through adolescence using Generalised Estimating Equations. Linear regression analyses examined associations between travel pattern (consistently passive, consistently active, active at two time points or active at one time point), BMI, and DXA-measured fat mass (expressed as internally derived standard deviation scores) at 17 years. Analyses were adjusted for height (where appropriate), sex, age, parental social class, and maternal education with interaction terms to assess sex differences. Results: There was substantial tracking in active travel through adolescence, with 38.5% of males and 32.3% of females consistently walking or cycling to school. In males, a consistently or predominantly active travel pattern was associated with a lower BMI SD score at age 17 (consistently active: adjusted β=-0.23; 95% CI -0.40, -0.06; active at two time points: adjusted β-0.30; 95% CI -0.50, -0.10) compared to those with a consistently passive pattern. No associations were seen in females. Conclusions: Maintenance of active travel behaviours throughout adolescence may help to protect against the development of excess BMI in males. In addition to encouraging the adoption of active travel to school, public health messages should aim to prevent drop out from active travel to promote good health in youth.
    Full-text · Article · Oct 2015
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    • "well within the recommended ACSM range. Given the benefits that exercising within this range has been shown to elicit [39-41], it is crucial to identify how individuals can be encouraged to work at this intensity. The current study examined the exercise intensity of self-selected exercise in adolescents, and although a different population from previous studies, results indicated that self-selected exercise intensity was within the recommended range of between 50-85% "
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    ABSTRACT: Background Positive affective responses can lead to improved adherence to exercise. This study sought to examine the affective responses and exercise intensity of self-selected exercise in adolescent girls. Methods An observational study where twenty seven females (Age M = 14.6 ± 0.8 years) completed three 20-minute exercise sessions (2 self-selected and 1 prescribed intensity) and a graded exercise test. The intensity of the prescribed session was matched to the first self-selected session. Intensity, affective responses and ratings of perceived exertion were recorded throughout the sessions and differences examined. Repeated measures ANOVAs were conducted to examine differences. Results There were no significant differences in intensity between the prescribed and self-selected sessions, but affective responses were significantly more positive (p < .01) during the self-selected session. Ratings of perceived exertion were significantly lower (p < .01) during the self-selected session than the prescribed session. On average participants worked at 72% V˙O2 peak; well within the intensity recommended by the American College of Sports Medicine. Conclusion Even though the intensity did not differ between the self-selected and prescribed sessions, there was a significant impact on affective responses, with more positive affective responses being elicited in the self-selected session. This highlights the importance of autonomy and self-paced exercise for affective responses and may have potential long-term implications for adherence.
    Full-text · Article · Oct 2014
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