This is a thorough review on the literature of walking that helps assist in the problem for "health professionals [who] are presented with the challenge of prescribing physical activity that is likely to be sustained by the sedentary majority".
The review provides this summary:
Walking has the potential to play a key role in the primary and secondary prevention of cardiovascular disease. Clinicians can prescribe walking to assist patients meet physical activity recommendations and help identify supports available to the patient.
Evidence from epidemiological studies suggest that even small improvements in the amount of daily walking is better than no walking, and greater increases confer larger cardiovascular health benefits. Patients may accrue short-terms gains such as improved fitness, body composition, blood pressure and lipid profiles. Longer term benefits include reduced risk of CHD, coronary events and mortality. Patients should gradually raise their walking levels, with the public health recommendation of 150 minutes per week as a minimum goal.