Just two weeks of a couch potato lifestyle increases the risk of serious disease, research has suggested.
Experts found that 14 days of sitting around reduces muscle mass, increases body fat and raises the potential for high cholesterol.
Taking 10,000 steps a day - widely regarded as a target for maintaining good health - should be something people strive for, they said.
The team, from the University of Liverpool, followed a group of 28 healthy people of a normal weight with an average age of 25.
Participants usually took 10,000 steps per day or more but did not have more than two hours of structured exercise - such as going to the gym or playing sport - per week.
For 14 days, people wore a SenseWear armband, which lets researchers track levels of physical activity, steps, sleep and lifestyle.
The group also had health checks on things such as fat, muscle mass and physical fitness at the start and the end of the study.
Dr Arif Rajpura, director of public health at Blackpool Council, said: “Most people know that doing more exercise will make you healthier. It reduces your risk of Type 2 Diabetes, heart disease and cancer, while it is also proven to have mental health benefits, making you happier.
“Being more active doesn’t have to mean running a marathon; it could be getting off the bus one stop earlier or taking a short walk in the evening.
“There are lots of simple ways to become more active. Our Steps to Health programme facilitates older people going on group walks around Blackpool, while the Making Changes programme helps to create a support plan for families to start doing more exercise.”
For more information on each of the council’s programmes, visit blackpool.gov.uk or speak to your GP.