Evidence for physical activity guidelines as a public health intervention: efficacy, effectiveness, and harm - a critical policy sciences approach

Background: Evidence for the efficacy of physical activity in conferring health benefits is unequivocal, and this has led national governments to produce guideline recommendations for physical activity levels in their populations. Aim: To evaluate how far evidence for the efficacy, effectiveness and comparative effectiveness of current physical activity guideline recommendations as a public health intervention is considered in developing guideline recommendations, including a consideration of the extent to which, in comparison to alternatives, they may result in harm. Methods: Utilising a critical policy sciences approach, national physical activity guideline recommendations in Australia, the UK and the USA, and those of the World Health Organisation, are examined, along with their stated underlying evidence bases, to analyse what evidence has been considered, how it has been interpreted, for what purpose, and with what outcomes. Results: All current guidelines recommend 150 minutes of moderate physical activity per week. However, efficacy evidence shows 60 minutes is sufficient to provide some health benefits. None of the guidelines considers effectiveness evidence nor potential effectiveness. No evidence could be found for the effectiveness of a recommendation of 150 minutes in improving population health, and none of the guidelines considers whether a recommendation at a lower but still sufficient level of efficacy (e.g. 60 minutes) would be a more effective public health intervention. Conclusions: Evidence considered in drawing up physical activity guidelines relates only to the efficacy of physical activity in conferring health benefits. The lack of effectiveness evidence, the failure to consider potential effectiveness, and related un-evidenced value judgements call into question the claim that the guidelines are evidence-based. Because neither effectiveness nor comparative effectiveness is considered, it is possible that current guidelines of 150 minutes may result in net harm to population health in comparison to the opportunity cost of recommendations at alternative levels.