Sufficient and Necessary

When I attended Dr. Jakicic's lecture last week, I wanted to point out one of the necessary components for addressing obesity that he did not include in his closing thoughts.
I thought of it again today as I recalled my studies as a Master's student last decade (2004-07).  I believe it was in a class that discussed disease etiology - or the processes that occur and lead to an illness.  Some things are necessary for a disease to occur, some of them are sufficient to cause the disease on their own and others only cause disease in the presence of some additional necessary factor.  
One example; Smoking.  Cigarette smoking is sufficient to cause lung cancer on its own but smoking is not necessary for lung cancer to occur.  Some people who never smoke also get lung cancer.  Sun burns may be necessary for one to get a certain type of skin cancer(but not sufficient).  DNA damage must also occur.  ETC

So Dr. Jakicic ended his presentation by saying that in order to address obesity, several disciplines need to work together. 
On the individual level, people who special in behavior modification or health coaching can work on motivating and supporting persons who are interested in losing weight.  Actually, they may even create programs to move people from not wanting to lose weight to making plans to change their lifestyle so they will.  Exercise specialists or kinesiologists stress the importance of physical activity as advised by the Physical Activity Guidelines.  This PA is not primarily for weight loss but for reducing the adverse consequences associated with being overweight.  Nutrition professionals encourage caloric modification and the adoption of the recommendations made in the Dietary Guidelines - foods to limit and foods to include.
[btw -reducing calories is sufficient for weight loss]
The piece that was left out is the one that is of most interest to me as a student and future researcher/policy analyst.
The missing piece is modifying the environment in which people find themselves so that the suggestions of the exercise and nutrition folks can actually be adopted.  The availability of healthy foods and food information and opportunities to be physically active and to sit less, at school, work, within faith communities,  restaurants, community places, etc.
This last piece is not enough - it is not sufficient, but it is absolutely necessary.  
We need the opportunity to use the skills and apply the knowledge - that's my passion.  I am not telling people what to do, but making it possible for them to do the right(healthy) thing, should they want to.