Doctors have hit on a cunning plan to transform fatties into slimline wonders: stop sending emails.

Health experts believe millions of hours of vital exercise are being lost every week thanks to the explosion in electronic messaging.

Once we walked to a colleague's desk to pass on a filthy joke or reveal what the boss and his secretary were doing in the photocopier room for three hours during the office Christmas party. Now it is easier to tap a short note on the computer, hit the send button and the world knows in seconds what has happened. It's great for gossip: bad for the figure.

As a result, Sport England, as part of its Everyday Sport campaign, is launching Email-Free Friday this week. Employers, it says, should introduce a ban on internal emails and get staff walking around their office - presumably to complain that they can no longer send emails.

'We're losing millions of hours of exercise through the explosion of email,' said Dr Dorian Dugmore, a health adviser to Sport England. 'People email colleagues who sit next to them, never mind those who work on the other side of the office. We have to change people's lazy attitudes.' Increasing activity levels by 10 per cent could save 6,000 lives and £500 million per year, as well as leading to one million fewer obese people in England, it is argued.

The idea also reveals a growing antagonism felt by many bosses to electronic messaging. John Caudwell, chief executive of Phone 4u, has banned his 2,500 staff from using email in the office.'We have email paralysis,' he said. 'If you have a cancer, you have to cut it out.'

· Those interested in Email-Free Friday can learn more on www.everydaysport.com, although they may prefer, in keeping with the project's ideals, to call in person at Sport England, Victoria House, Bloomsbury Square, London WC1.