San Francisco for Common barriers to change facing people within the same stage this idea would be helpful in encouraging progression through the stages if people at one stage have to address similar issues, for example if low self-efficacy acted as a common barrier to the initiation of dietary change. . Different barriers to change facing people in different stages if the factors producing movement to the next stage were the same regardless of stage e.g. self-efficacy, the same intervention could be used for all, and the stages would be redundant. Ample evidence exists that barriers are different in the different stages see below. The transtheoretical model TTM This model was developed by Prochaska and di Clemente to address intentional behavioural change. San Francisco 2016.