Plainly the ideal is to examine life style critically and try to alter it but the car, the computer screen, the fear of attack on the street, the lack of recreational resource, the temptation of the fast food store and the small screen are part of the lives of many people in the 21^st century. They will not go away or change quickly.What advice is reasonable for 21^st century man and woman? What is the evidence?

To maintain moderate fitness - I.e. to climb a flight of 20 stairs, quickly, easily and without becoming breathless or to have to stop, to be able to walk 1 kilometre on the flat without effort.
Exercise every day or at least five times a week.
Exercise for at least half an hour per day.
Exercise is pleasant and enjoyable.
Exercise that can be easily incorporated into daily living - not taking the lift, parking the car further away, washing the car and not using the car wash, regular golf, swimming, tennis, bowls, dancing, walking, cycling or some pragmatic and pleasant mixture.