It is interesting that the behavior change model that is commonly used in smoking cessation is the very same one that fitness professionals are encouraged to use in determine where someone is in terms of adopting health promoting habits. It is Prochaska’s and DiClemente’s Transtheoretical Stages of Change model.
As you are likely aware a person who is not ready to change a particular behavior is termed a precontemplator. This is true for someone who doesn’t want to stop smoking but wants to engage in physical activity. His/her readiness and commitment to engage in physical activity may be different than his or her commitment and readiness to stop smoking.
When the readiness, commitment and confidence to change a behavior (as far as quitting smoking and beginning a health-promoting behavior) is relatively equal, it will give you a clue as to when to help the client create a goal of either quitting smoking or engaging in physical activity. Knowing when to incorporate either goal is dependent upon where they are as far as changing the behavior is concerned.
Professionally, I would use coaching strategies in order to determine where the client is on the “stages of change continuum with both goals and incorporate one of the other when the readiness, commitment and confidence are high. What I mean by “high” is utilizing a tool such as a Likert scale to determine readiness, commitment and confidence. In this way the individual will be successful with his or her goals.
I hope this is helpful.