It is not necessary to complete a punishing workout at a gym to stay healthy, experts have said.
Activity does not have to be strenuous
The Health Development Agency (HDA) said physical activity that fits into people's everyday lives may be more effective.
Simply walking instead of taking the car or playing active games with children can help, the government agency said.
Around three in four women and three in five men do not take enough exercise.
The HDA believes there is a desperate need to get people in the UK to do more exercise as increasing levels of obesity risk growing levels of cardiovascular disease and other ill health.
HDA advice on getting active
Take the stairs or walk up escalators
Walk to the next bus stop
Leave your car at home for short journeys
Play active games with your children
Try dancing or gardening
Get active in the bedroom
Active people have a 50% lower risk of heart disease and regular exercise plays a role in tackling obesity, diabetes, osteoperosis and colon cancer.
GPs are now providing people with information about exercise, and programmes are available for people to do physical activity at home with telephone support from an adviser.
Paul Streets, chief executive of the HDA, said: "Many people waste energy feeling guilty for not going to the gym, when instead they should think about what activity they can do easily and just do it. The key is tailoring the activity to the individual, whatever the age or ability."
He advised taking exercise for at least 30 minutes, five days a week, though this can be broken into shorter periods.
Public health minister Melanie Johnson said: "We want people to recognise that increasing physical activity does not necessarily mean pumping iron at the gym, but undertaking activities like walking a bit more, using the stairs rather than the lift or gardening."
The HDA's message was supported by David Jones, professor of sport and exercise science at the University of Birmingham, though he warned campaigns can have a limited effect.
Professor Jones said: "If you want to become fit for a 1,500m race or a marathon, you do need to train very hard. But if you want to stay fit to stay alive, it is very likely that light activity helps."