For most people, modification rather than elimination is all that is needed when it comes to changing ones diet or physical activity levels. Unlike stopping smoking, for example, there is no "quit day" when it comes to behavioural change linked to exercise and nutrition. There may of course be targets...for example, to exercise 5 x a week, each 5 fruits and vegetables a day or to make changes to reduce risk factors that may result in high blood pressure, diabetes or heart disease ( particularly for secondary prevention). For the latter to be successful, the behavioural change needs to be for a lifetime not just the long term. Long term change can be daunting as people have to come to grips with the chronic nature of their condition. It seems like the person is now faced with overwhelming burden...they have to give up or restrict favourite foods and/or reduce a sedentary lifestyle. Such changes can manifest themselves as withdrawal. Sometimes it's necessary to reframe the changes into positive terms. What's the benefit of doing nothing and maintaining the status quo vs making the changes that may be life saving. At this point, the resisters will focus more on their dislike of avocados rather than the bigger picture. Rather than "yes, of course I will do more cardio," it's often "if you think I am giving up chocolate…dream on!”
The use of motivational interviewing techniques rather than straight forward advice (ie. eat more of this or that) has been identified to be more beneficial. Individuals undertaking these interventions had better results, attended counselling more frequently and were more compliant with self monitoring of their health. A lot can depend on who is delivering the motivational interviews. In some cases it may be best if advice comes from people with a background in counselling rather than exercise professionals or dieticians.
As a personal trainer, I supply information on a drip feed style. A bit here and there, nothing too complicated. I don't want to overwhelm clients! I like to encourage clients to take ownership of their own health and then work to facilitate changes with various adherence methods. It may take time for the client to see the benefits of the change and accept that that is what they have to do.
People resist change in all aspects of life. I get it... it's uncomfortable. If we can identify the benefits and show what happens if change doesn’t happen, then we can work towards inspiring the client in altering their lifestyle.