Believe me exercise and healthy diet is not the 'cure all' for Anxiety in some of us.
I have one of the most healthy, balanced diets of anyone i know, i ride my bike 10 miles per day and have been for 8 years yet still suffered with crippling Anxiety & Depression.
This was before id discovered Benzos, so my symptoms were not Benzo related.
By all means a healthy diet and exercise is a good thing but it's not the magic bullet like 99% of people seem to suggest.
Btw im not trying to say long term Benzo use will not exacerbate your Anxiety, it probably will, just dont be too disappointed if the healthy diet/exercise regime doesnt work as well as many people make out.
Best of luck to you in trying to overcome your problems.