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Physical activity and obesity editorial: is exercise pointless or was it a pointless exercise?
  1. Kamal R Mahtani1,
  2. Jim McManus2,
  3. David Nunan1
  1. 1 Centre for Evidence Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
  2. 2 Department of Public Health for Hertfordshire and Academy of Medical Royal Colleges Health Inequalities Forum member, Hertfordshire County Council, Hertford, UK
  1. Correspondence to Dr Kamal R Mahtani, Centre for Evidence Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, UK; kamal.mahtani{at}

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In their editorial, Malhotra et al 1 highlighted the important health benefits of physical activity in cardiovascular disease, type 2 diabetes, dementia and cancer, but dismissed any benefit for weight loss in obesity. However, the poor use of existing evidence to underpin this dismissal and the resultant press release generated headlines that could send a misleading message to patients and the public.

Poor use of evidence

An evidence-based approach to clinical decision-making involves understanding the best type of evidence to use, how to appraise it, and assessing its usefulness in practice. Such an approach determines the risk of bias and ensures decisions are guided by accurate, meaningful evidence. The GRADE guidelines cite expert opinion alone as very low quality evidence, with a high risk of bias.2 Unfortunately, much of the evidence cited by Malhotra and colleagues was based on expert opinion or was not referenced. For example, when excluding a relationship between obesity and physical activity, the evidence cited was an opinion piece by Luke and Cooper,3 which has been criticised for ignoring observational and experimental studies that support a relation between physical activity and obesity. They give no reference for their claim that, according …

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