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In children and youth, regular physical activity and adequate diet are necessary for normal growth and they impact a range of health outcomes1 including overweight and obesity. Children are a critical target group for public health efforts to prevent overweight and obesity. Key elements to prevent excess bodyweight are physical activity, sedentary time and a healthy diet. Several structural changes during the past decades have led to changes in these behaviors. It is easy to make the unhealthy choices and gain excess bodyweight. Thus, effective interventions to promote physical activity and a healthy diet are essential.
The health in adolescents (HEIA) study
In a related paper, Grydeland et al2 report results from a systematically developed 20-month cluster randomised controlled school-based intervention—the HEalth In Adolescents (HEIA) study—on body composition outcomes. The HEIA study has previously reported intervention effects on targeted behaviours like time spent watching TV/DVD, computer/game use, consumption of sugar-sweetened beverages and physical activity (objectively measured). The intervention increased overall physical activity among the participants; its benefit was greatest among girls and low-active participants. In the related paper the authors report significant beneficial effects on BMI and BMI-for-age z-scores in girls.2
These results on body composition outcomes are promising. However, no intervention effects were seen among boys or among participants of parents with lower levels of education. There appear to be some reasons why the impact was not better and did not reach boys. Low cost and applicability in the public school system had high priority in the HEIA study, and the intervention components were primarily delivered through the school teachers and dependent on their devotion. Even with ambitious goals for what activities the children should engage in, the impact depends on what the children actually do. In a recent meta-analysis, Metcalf3 concluded that physical activity interventions have little effect on the overall activity of children, which may explain, at least in part, why such strategies have had limited success in preventing childhood obesity.3 There is no reason to believe that this conclusion is wrong. However, it is tempting to argue that physical activity intervention at school will have an impact if it is received. Just like when patients take their medications a treatment may work, if they do not, the treatment does not work. The challenge is to implement physical activity and a healthy diet with strong enough impact.
What are the practical implications?
Do we have enough evidence to implement physical activity and nutrition advice in the school-setting? I would say yes! The school is an important setting, because it represents the only available arena where all children, irrespective of social background, can be reached continuously over a long period of time. The prevalence of non-communicable diseases (NCD) is increasing worldwide, and such NCDs affect people of all ages, including children.4 The best means to deal with this immense problem are through primary prevention, and physical activity and healthy eating are powerful determinants that play key roles in preventing a host of NCDs. Moreover, healthy habits learned in childhood are likely to persist into adulthood. Children who are physically active during childhood and adolescence are more likely to be physically active as adults.5
There are, however, crucial barriers to overcome when we want to implement strategies to increase physical activity and to improve nutrition. Probably the most important is the willingness of the decision makers to prioritise this over a long period of time. Political will. If they commit to the health of their constituents, then it should be commonplace to have 45 min/day of physical activity and rare not to. It should even be possible to introduce daily physical activity in the curriculum and to make structural changes to promote healthy eating without hindering student academic achievement. Some would argue that time spent in physical activity will improve overall academic performance. However, to succeed a program must be anchored in the educational mandate at national, regional and local level. If there is just lipservice and half-hearted whitewashing, the likely outcome is an increase in social inequalities rather than a reduction in them.
Footnotes
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Competing interests None.
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Provenance and peer review Commissioned; internally peer reviewed.