New efforts are being led by the nation’s medicines watchdog to try and get Britons to exercise more.
Lack of exercise causes the same level of ill health that smoking does, experts said, but despite this only a minority of people in England get enough exercise.
The National Institute of Health and Clinical Excellence (NICE) has issued new guidance to encourage local authorities, schools, workplaces and other institutions to get more people active.
Strategic and scientific adviser to the National Obesity Observatory, Dr Harry Rutter, who worked on the new guidance, said: “Only a minority of people in England get enough physical activity to improve their health.
“This creates a huge and often invisible burden of illness and reduced quality of life, but most people seem unaware of that burden.
“Across the population, lack of physical activity causes roughly the same level of ill health that smoking does.
“We all face barriers in changing our lifestyles and many of us feel we don’t have the time or the inclination to add regular physical activity into our lives - it can be very difficult to break old habits and change behaviour.
“But walking and cycling to work, to school, to the shops or elsewhere can make a huge difference.
“This guidance aims to help people in local authorities, public health professionals, schools, workplaces, the NHS and many others to make the changes that are needed to support this safe, healthy and mostly enjoyable physical activity.”
He added: “We have a silent epidemic of lack of physical activity and here we have a wonderful opportunity to try and do something about it.”
The guidance states that walking and cycling should become the norm for short journeys and should be encouraged in local communities.
Adults should be doing at least 150 minutes of moderate intensity activity every week, in bouts of 10 minutes or more.
Local communities should implement schemes to encourage more people to cycle and walk, the guidance states. They could include “car free days” or cycle-hire schemes - such as the “Boris bike” initiative in London.
Local authorities could create special signage showing distances and walking times, according to the Nice recommendations.
Transport planners should also examine traffic volumes and speed limits which discourage people from walking and cycling.
Schools should galvanise pupils to be more active by initiating walking groups and “walking buses”, the guidance suggests.
Professor Nanette Mutrie, chair of physical activity for health at the University of Edinburgh, said: “I feel the risks of being inactive have perhaps been underestimated by most people.
“The fact that inactivity is the fourth leading cause of premature death worldwide is probably not recognised by most people.”
Professor Mike Kelly, director of the Centre for Public Health Excellence at NICE, added: “Two-thirds of the population isn’t active enough.
“Walking and cycling is an easy way to get active - it is a form of both getting places that you need to and also a form of recreation.
“This guidance is aimed at making it easier for people to do this, as well as explaining the benefits and helping to address some of the safety fears that some people may have.”