30 minutes' exercise may not stop weight gain, says doctor

Taking a recommended 30 minutes' exercise a day may not stop you from putting on weight, a major conference on obesity was told yesterday.

Dr Donal O'Gorman, a member of the National Task Force on Obesity, said public health bodies should now be recommending 60-90 minutes' exercise a day in light of research showing the 30-minute threshold to be inadequate.

Dr O'Gorman, a lecturer in Dublin City University's centre for sports science, said: "We have accepted 30 minutes' of physical activity as a one-size-fits-all solution to health.

"Thirty minutes is OK for general health and to reduce the risk of cardiovascular disease. But more is needed to prevent weight gain."

Delegates at the all-Ireland conference, Tackling Obesity Together, which is taking place over two days in Co Cavan, expressed concern that a new recommendation in the area would confuse the public, if not damage confidence in public health communications.

However, Dr O'Gorman said: "I think the evidence is strong enough to look at a recommendation now. We should spell out there is a difference between what is good for general health, and what is good for preventing weight gain.

"When we talk about an hour's exercise it's throughout the day. It does not mean a 60 or 90 minute walk."

He said guidelines had already been revised in the US, Canada and the UK.

In the case of the latter, the British chief medical officer said this year that "for many people" 45-60 minutes of moderate intensity physical activity was necessary to prevent obesity. However, people who had been obese and managed to lose weight could need 60-90 minutes activity per day to avoid regaining weight.

Dr O'Gorman said: "We need to take a step back and look at what's best for the individual condition rather than take a minimalist approach."

He noted research showed people needed to burn 500 kcals of energy daily to maintain their body weight. Thirty minutes' of moderate exercise burnt just 200 kcals.

A separate DCU survey of physical activity among 15-17 year-olds in Dublin showed 17 per cent were overweight and 5 per cent obese.

Dr O'Gorman said more girls than boys failed to meet recommended activity levels.