Sedentary behaviour (e.g. TV viewing, seated video game playing, prolonged sitting) has recently emerged as a distinct risk factor for cardiometabolic diseases in children and youth. This narrative review provides an overview of recent evidence in this area and highlights research gaps. Current evidence suggests that North American children and youth spend between 40% and 60% of their waking hours engaging in sedentary pursuits. Although data are lacking concerning temporal trends of objectively measured sedentary time, self-reported sedentary behaviours have increased over the past half century, with a rapid increase since the late 1990s. Excessive sedentary behaviour has been found to have independent and deleterious associations with markers of adiposity and cardiometabolic disease risk. These associations are especially consistent for screen-based sedentary behaviours (TV viewing, computer games, etc), with more conflicting findings observed for overall sedentary time. The above associations are possibly mediated by the influence of screen-based sedentary behaviours on energy intake. Although excessive sitting has been reported to have adverse acute and chronic metabolic impacts in adults, research on children is lacking. Research is particularly needed to investigate the impact of characteristics of sedentary behaviour (i.e. type/context, sedentary bout length, breaks in sedentary time, etc), as well as interventions that examine the health and behavioural impacts of sitting per se.
To examine the independent relation of physical activity (PA) and cardiorespiratory fitness (fitness) with measures of obesity in Mexican children.Children (N=193) in 5th and 6th grade from Guadalajara participated. Body mass index (BMI), sum of skinfolds (SS) and waist circumference (WC) were measured. PA was measured over four days using pedometry and fitness was measured using the 20 meter shuttle-run test.Fitness and PA were negatively related to the obesity measures in boys and girls (r=-0.57 to -0.64 and r=-0.18 to -0.23 respectively). Age adjusted significant differences in WC, BMI, and SS were observed between the lowest and highest fitness tertiles for boys and girls (p<.01). Age, gender, and PA adjusted fitness explained 23 to 34% of the variance on WC (r²=0.23, p<.01), BMI (r²=0.23, p<.01), and SS (r²=0.34, p<.01).Fitness is a stronger correlate and better predictor of obesity than PA in this sample.
No abstract is provided for this article.
Thirty cross-trained, female subjects (19-69 years) completed an endurance exercise session (ES), a resistance exercise session (RS), and a control session (CS) in a randomized, balanced design. The ES consisted of 40 minutes of cycling at 75% maximum heart rate, and the RS consisted of 3 sets of 10 repetitions of eight exercises. During the CS, subjects performed no exercise. Before and after exercise, and after 30 minutes of recovery, blood samples were analyzed for plasma lactate and serum growth hormone, insulin-like growth factor 1, testosterone, estradiol, dehydroepiandrosterone, and cortisol. Samples were taken during the CS at the same intervals as during the exercise sessions. There were no age-related differences in intensity measures during exercise. Absolute change from baseline in testosterone (p <.001), estradiol (p <.05), and growth hormone (p <.01) was significantly greater in the ES and RS compared with that in the CS. Absolute change in dehydroepiandrosterone was significantly greater in the RS only (p <.05). Results indicate that an acute bout of exercise can increase concentrations of anabolic hormones in females across a wide age range.
We believe that there is little to be gained by arguing with Roland Auer and colleagues about whether diet or physical inactivity is the most important variable leading to obesity in Canadian children: together these factors determine caloric balance and therefore both are important. We advocated
Tremblay (mtremblay@cheo.on.ca) is with the Healthy Active Living and Obesity Research Group, Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada. Gonzalez is with the Dept of Public Health, School of Medicine, Universidad de los Andes, Bogota, Colombia. Katzmarzyk is with the Pennington Biomedical Research Center, Baton Rouge, LA. Onywera is with the Dept of Recreation Management and Exercise Science, Kenyatta University, Nairobi, Kenya. Reilly is with the Physical Activity for Health Group, School of Psychological Sciences and Health, University of Strathclyde, Glasgow, Scotland. Tomkinson is with the Alliance for Research in Exercise, Nutrition, and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, South Australia, Australia. Physical Activity Report Cards: Active Healthy Kids Global Alliance and the Lancet Physical Activity Observatory