Six hours of exercise a week is ‘best dose to ward off disease’

    12 August 2016

    The minimum amount of exercise recommended by the British Government and the World Health Organisation is insufficient to prevent cancer, stroke, heart attacks and diabetes, according to a study published in the British Medical Journal.

    The researchers, from the University of Washington and the University of Queensland, say that exercising for more than six hours a week gives you the best chance of avoiding these conditions.

    Current WHO advice says that adults should do either two and a half hours of moderate exercise, or an hour and 15 minutes of vigorous exercise a week. But the researchers believe this is far too little.

    They looked at 174 studies examining the association between physical activity and the five major diseases. They found that the greatest health gains occurred when total weekly activity was between 12 and 16 hours of moderate activity — anything from gardening to walking to doing household chores — or between six and eight hours of vigorous exercise such as running.

    At this level, the risk of breast cancer fell by five per cent, heart disease risk dropped by 20 per cent, stroke, and diabetes and colon cancer risk dropped by a sixth. More hours of exercise beyond this point failed to provide any further benefits.

    The study’s authors wrote: ‘With population ageing, and an increasing number of cardiovascular and diabetes deaths since 1990, greater attention and investments in interventions to promote physical activity in the general public is required.

    ‘More studies using the detailed quantification of total physical activity will help to find a more precise estimate for different levels of physical activity.’

    Instant analysis
    This is a systematic review and dose-response meta-analysis using data from 174 articles which looked at links between total physical activity and risks of breast cancer, colon cancer, diabetes, ischaemic heart disease and ischaemic stroke events. Physical activity was measured in terms of energy output — specifically, the number of metabolic equivalent (MET) minutes a week. (One MET is the amount of oxygen consumed while sitting at rest in a minute.)

    The study found that higher levels of exercise were associated with lower risk for all outcomes, but that the main impacts occurred at around 3,000-4,000 MET minutes/week. So, people at 600 MET minutes/week of physical activity (the minimum recommended level) had a 2 per cent lower risk of diabetes compared with those who reported no physical activity. But an increase from 600 to 3,600 MET minutes/week showed a reduction in the risk by an additional 19 per cent.

    There were smaller returns at higher levels of activity: an increase from 9,000 to 12,000 MET minutes/week was associated with only 0.6 per cent reduction in diabetes risk.

    The study cannot draw definite conclusions about cause and effect, nor can it tell us about what types of exercise are better, but the idea that doing more exercise reduces disease risk is hardly shocking. What is perhaps more concerning is that many people are not even reaching those recommended minimum levels of activity. The real challenge is how we get people to start doing more.
    Research score: 3/5