Increased sedentary time from childhood to adolescence is directly linked to childhood obesity, but new research has found that light physical activity can completely reverse the adverse process.
Summary Effects of accelerometer-based sedentary time and physical activity on fat mass measured with DEXA in 6059 children Globally, childhood obesity is increasing and the effect of objectively measured movement behavior on body composition remains unclear. Longitudinal and causal mediation relationships of accelerometer-based sedentary time (ST), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) with fat mass measured by dual-energy X-ray absorptiometry were examined in 6059 11-year-old children followed to age 24 from the Avon Longitudinal Study of Parents and Children (ALSPAC), UK birth cohort. Over a 13-year follow-up, each minute/day of sedentary time (ST) was associated with a 1.3 g increase in fat mass. However, each minute/day of light physical activity (LPA) was associated with a 3.6 g decrease in fat mass and each minute/day of moderate to vigorous physical activity (MVPA) was associated with a decrease of 1. 3 g in the fat mass. Persistent accumulation of ≥60 min/day of MVPA was associated with a 2.8 g decrease in fat mass per minute/day of MVPA, mediated in part by a decrease in insulin and low-density lipoprotein cholesterol. . LPA elicited a similar and potentially stronger fat mass-lowering effect than MVPA and may therefore be a target in the prevention of obesity and TS in children and adolescents who are unable or unwilling to exercise. |
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The study, conducted in collaboration with the University of Exeter, the University of Eastern Finland, the University of Bristol and the University of Colorado and published in Nature Communications , is the largest and longest follow-up to objectively measure physical activity and mass fat , using children’s data from the 1990s from the University of Bristol (also known as the Avon Longitudinal Study of Parents and Children ). The study included 6,059 children (53 percent female) aged 11 years who were followed until age 24 years.
Recent reports concluded that more than 80 percent of adolescents worldwide do not meet the World Health Organization’s (WHO) recommended average of 60 minutes of moderate to vigorous physical activity daily. It is estimated that physical inactivity will have caused 500 million new cases of heart disease, obesity, diabetes or other non-communicable diseases by 2030, costing £21 million a year. This alarming prediction about the morbid danger of physical inactivity calls for urgent research into the most effective preventive approach.
However, the results of this new study show that moderate to vigorous physical activity is up to ten times less effective than light physical activity in decreasing overall fat mass gain.
Dr Andrew Agbaje from the University of Exeter led the study and said: “These new findings strongly emphasize that light physical activity may be an unsung hero in preventing fat mass obesity from the first years of life. It’s time for the world to replace the mantra of “an average of 60 minutes a day of moderate to vigorous physical activity” with “at least 3 hours a day of light physical activity.” “Light physical activity seems to be the antidote to the catastrophic effect of sedentary time in the young population.”
During the study, a waist-worn accelerometer measured sedentary time, light physical activity, and moderate-to-vigorous physical activity among participants ages 11, 15, and 24. Fat mass and skeletal muscle mass measured by dual-energy low density, triglycerides and high sensitivity C-reactive protein. Additionally, blood pressure, heart rate, smoking, socioeconomic status, and family history of cardiovascular disease were measured and controlled for in the analyses.
Over the 13 years of follow-up, sedentary time increased from about six hours a day in childhood to nine hours a day in adulthood. Light physical activity decreased from six hours a day to three hours a day, while moderate-to-vigorous physical activity remained relatively stable at around 50 minutes a day from childhood to adulthood.
It was observed that each minute of sedentary lifestyle was associated with an increase of 1.3 grams in total body fat mass.
Both boys and girls gained an average of 10 kg of fat mass during growth from childhood to adulthood. However, sedentary time potentially contributed 700 grams per 1 kg of fat mass (approximately seven to ten percent) of the total fat mass gained during growth from childhood to adulthood. An increase of 1 kg of fat has been linked to a 60 percent increased risk of premature death in a 50-year-old person.
Every minute spent in light physical activity during growth from childhood to adulthood was associated with a 3.6 gram reduction in total body fat mass. This implies that cumulative light physical activity decreased total body fat mass by 950 grams to 1.5 kg during growth from childhood to adulthood (approximately a 9.5 to 15 percent decrease in overall gain of fat mass during the 13-year observation period). Examples of light physical activity are long walks, housework, slow dancing, slow swimming, and slow cycling.
In contrast, time spent in moderate to vigorous physical activity (including meeting the WHO-recommended 60 minutes per day) during growth from childhood to adulthood was associated with a reduction of 70 to 170 grams (approximately 0.7 to 1.7 percent) in total body fat mass. Before this study, it had not been possible to quantify the long-term contribution of sedentary time to fat mass obesity and the magnitude by which physical activity can reduce it. But this study confirmed the report from a recent meta-analysis of 140 randomized controlled trials in schools around the world that engaging in moderate to vigorous physical activity had little or no effect on reducing BMI and childhood obesity.
Dr Andrew Agbaje from the University of Exeter said: “Our study provides novel information that would be useful in updating future health guidelines and policy statements. “Public health experts, health policymakers, health journalists and bloggers, pediatricians, and parents should encourage continued and sustained participation in light physical activity to prevent childhood obesity.”
Reference : ’Effects of Accelerometer-based Sedentary Time and Physical Activity on DEXA-measured Fat Mass in 6059 Children’ published in Nature Communications.
