Increased physical activity improves metabolic health, independent of time spent sedentary
MedWire News: Results of a study published in JAMA suggest that children should be encouraged to increase their participation in physical activity, rather than reducing their time spent sedentary, to improve their cardiovascular health.
Many public health authorities and organizations have compiled guidelines suggesting that children should reduce the amount of time spent sedentary, especially viewing TV, write Ulf Ekelund (Addenbrookes Hospital, Cambridge, UK) and colleagues.
However, the teamfound that increased time spent participating in moderate-to-vigorous physical activity (MVPA) was associated with improved cardiometabolic outcomes regarding waist circumference, systolic blood pressure, fasting triglycerides, high-density lipoprotein (HDL) cholesterol, and insulin, regardless of the amount of time spent sedentary.
Ekelund and co-investigators pooled data from 14 studies involving more than 20,000 children (aged 4-18 years). They then examined the independent and combined associations between physical activity and sedentary time, measured objectively by accelerometry, and cardiometabolic risk factors.
Overall, children spent 30 minutes per day in MVPA and 354 minutes per day sedentary.
Time in MVPA was significantly associated with all cardiometabolic outcomes, independent of age, gender, monitor wear time, time spent sedentary, and waist circumference. Conversely, time spent sedentary was not associated with any of the outcomes after additional adjustment for time in MVPA.
In combined analyses, higher amounts of time spent in MVPAwere associated with significantly lower values for waist circumference, systolic blood pressure, fasting insulin, and fasting triglycerides, and higher values for HDL cholesterol across tertiles of sedentary time.
Furthermore, the differences in outcomes between high (mean 52.5, range 20.6-185.0 minutes/day) and low (mean 12.0, range 0.0-27.2 minutes/day) tertiles of time spent in MVPA were greater the lower the sedentary time. For example, the mean differences between the high and low MVPA tertiles for waist circumference across sedentary categories varied between 3.6 and 5.6 cm.
"Moving from the bottom to the top tertile for MVPA requires an increase in MVPA of at least 20 minutes per day," write Ekelund et al. "Increasing daily activity at this intensity level can be achieved by participating in activities such as brisk walking, jogging, cycling, playing soccer, and other team sports."
The researchers note that although sedentary time was not independently associated with metabolic health, their measure of sedentary time takes into account the accumulated time spent sedentary rather than a specific behavior. They therefore stress that decreasing sedentary behaviors, such as TV viewing, should still be an important public health goal.
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By Nikki Withers