This summer, the government’s Department of Health and Social Care updated their Childhood Obesity Plan, announcing their ambition to halve childhood obesity by 2030. One of the measures promoted in the plan is the call for all primary schools to adopt initiatives, such as the Daily Mile. The programme, developed in a school in Scotland, involves all pupils in the school running or walking outdoors for 15 minutes per day (equivalent to around one mile on average).

The programme was introduced to improve children’s fitness levels, but was reported to also reduce how much time children spend being sedentary, improve their well-being, social interaction, concentration levels and to reduce obesity. Promoted by the Daily Mile Foundation and benefiting by support from the Scottish Government, the programme has gained popularity and momentum across many schools in the UK and internationally.

Higher levels of physical activity are associated with numerous benefits, including better fitness, physical and emotional health, and higher academic achievement. Being more physically active is also an important contributor to weight maintenance and obesity prevention. National and international guidelines recommend that children should spend a minimum of one hour a day being at least moderately active. However, surveys show that only around a fifth of children are sufficiently active and physical activity levels fall during the primary school years, particularly among girls. It therefore seems very reasonable to expect that a simple intervention that schools can deliver to increase children’s activity levels would be beneficial.

The Daily Mile motivates children to be more physically active through proven theoretical pathways, such as promotion of autonomy (empowering children to set their pace and teachers to choose when and how to run the programme), engendering a sense of belonging (inclusive of all children, connecting with others and their teachers) and achieving competence (simple skill that is easily achieved and sufficiently challenging). However, the Daily Mile does potentially reduce classroom time by 75 minutes each week, thus displacing other activities, the value of which is unknown. Therefore, it is important for the programme to be rigorously assessed to evaluate whether the expected benefits are realised in practice, whether any effects are equitably distributed and that there are no adverse effects (such as physical activity-related teasing), all offset against the cost of the displaced activities.

Several programmes to increase children’s physical activity levels in school have been previously evaluated. A high-quality systematic review of these has shown that such programmes increase physical activity levels during the school period and reduce the time that children are sedentary. However, their impact on overall physical activity levels is relatively small (between 5 and 45 minutes additional activity per week) and there is no evidence that the programmes reduce levels of obesity. Since the publication of this review, three large trials with over 5,000 children from almost 150 schools have evaluated different theoretically informed programmes targeting children’s diet and physical activity levels through school. None of the programmes, including a curricular-based educational intervention, a motivational programme incorporating drama and goal-setting and an experiential skill-based intervention, demonstrated any evidence of increasing children’s physical activity levels overall or in reducing obesity. The latter, the WAVES study, which was undertaken by our research team in Birmingham, included training teachers to incorporate an additional 30 minutes of at least moderate physical activity in the school day. School staff found this difficult to deliver and overall only managed to add 15 minutes of additional physical activity.

While some schools are able to deliver programmes successfully, others lack enthusiastic and supportive staff, reducing the impact of programmes and potentially leading to inequalities. When programmes are successfully delivered, compensatory behaviours, such as using unhealthy food treats as rewards, may dissipate any effects. The sustainability of any effect is also unclear as initial enthusiasm for programmes might waver over time. Furthermore, introduction of a physical activity intervention may replace rather than add to existing physical activity programmes within or outside of school.

The Daily Mile has potential benefits compared to previous programmes. It is relatively simple, has a single focus, involves the whole school and has the advantage of support from the government and much positive publicity. In addition to its potential to increase physical activity and reduce obesity, it could impact on children’s social and emotional well-being. Nevertheless, a rigorous evaluation is essential to assess whether this potential is realised and at what cost, and to assess the long-term acceptability of the programme as schools are measured on pupil academic performance, not physical fitness. The equity of the programme and potential for harm also need to be assessed. The University of Birmingham, in collaboration with Birmingham Services for Education and Birmingham City Council are currently evaluating the Birmingham Daily Mile, with 2,000 children from 40 schools participating to answer some of these questions.