Answer the following question in 250-350 words please

Program Adherence, as we know, is one of the biggest obstacles to achieving fitness goals and optimal health.  Everyone seems to be looking for that one thing that will help them get there. And, each year brings another set of Hot Fitness Trends that promise to deliver. Some of the currently popular trends include:

HIIT
Bodyweight training
Group Personal Training
In-Home Fitness
Wellness Coaching
Functional Fitness
Tactical Strength & Conditioning

First, why do you think that there always seems to be a new best program every year?  Is there a place for all of these trends?  How would you gently steer a client away from a popular trend that they may not be ready for? 
Then, explain how you can use Behavior Change Theory (such as S.M.A.R.T. Goals, Health Behavior Model, Transactional Leadership, the Stages of Change, etc.) to help improve Program Adherence.