The researchers from the Medical Research Council Epidemiology Unit also found significant positive results for multi-component interventions aimed at adolescents. These are programmes which along with traditional health education included policy or environmental changes, for example additional PE classes.
The authors say the programmes that work can make important differences and should be actively promoted.
The review, which looked at all the published literature on the effectiveness of promoting physical activity to children and adolescents, also found some evidence that programmes which change children's environments, for example, improving a playground, can have significant effects. Programmes aimed at children from lower socioeconomic backgrounds can also have some impact on activity levels. However, the researchers say both these areas need to be investigated more closely.
Increasing physical activity among young people has been identified as one of the key ways to tackle obesity. The authors say children who are inactive tend to remain inactive as adults, which means their risk of developing cardiovascular disease, cancer and osteoporosis in later life is increased. They argue this means developing and evaluating these sorts of programmes is therefore a priority. To date it has been unclear how successful efforts to increase the activity levels of young people have been.
The reviewers found no evidence that initiatives which use education alone had any effect on children's activity levels and there was inconclusive evidence of the benefit to adolescents.
The evidence for the benefit of programmes which used a variety of components, for example additional PE classes, PE teacher training or the availability of extra equipment, was found to be inconclusive for children. There was strong evidence however that this is an effective strategy for adolescents.
They found strong evidence to support the use of programmes where adolescents were involved in school-based initiatives but where the family or community had to become involved as well, for example, through homework assignments or incorporating physical activity into existing community events. The effects seen in the studies ranged from 3 minute increases during PE to a 50% increase in the number of participants being regularly active.
Overall they say there was stronger evidence for the effectiveness of physical activity programmes among adolescents, yet that could be because the studies were of higher quality and they also included large sample sizes. One of the reasons for the increased effectiveness among adolescents could also be that they are known to be less active than children so there could be greater potential for change.