The explosion in e-mail use risks creating a generation of unfit, overweight office workers, say experts.
A recipe for obesity?
Whereas white collar workers were once forced to walk to colleagues' desks to pass on information, now all it takes is the click of a button.
As a result, many people are missing out on the little exercise available to them during the working day.
Sport England is urging people to refrain from sending unnecessary messages this Friday.
They hope E-mail Free Friday will help to make people in sedentary jobs think about the need to keep active.
Dr Dorian Dugmore, an international heart expert, said: "We are losing millions of hours of exercise through the explosion of e-mail.
"The average energy expenditure of deskbound workers falls well below the recommended amount of 40 minutes per day.
"We are now all familiar with the five servings of fruit and vegetables every day and now it's time to start applying the same principle to our working lives."
Slave to the screen
Dr Dugmore said a "screen slave" culture had developed in many offices.
"People e-mail colleagues who sit next to them, never mind those who work over the other side of the office.
"It might seem like a small change to make, but we need to start somewhere in a bid to change people's increasingly lazy attitudes."
Dr Dugmore said the average person would take the escalator from the train station, catch the bus nearest to their office, take the lift to their office floor and spend more and more time sitting at their desks.
He said: "Increasing activity levels by just 10% could save 6,000 lives and £500million per year, and one million fewer obese people in England could mean 15,000 fewer people with coronary heart diseases, 34,000 people developing type 2 diabetes and 99,000 fewer people with high blood pressure."
Roger Draper, chief executive of Sport England, said: "We have a big task to increase the number of people who are physically active and what better place to focus our efforts than in the work place.
"We want to get people in offices, factories, supermarkets and hospitals on the move and building activity into their daily lives."