Chris nailed it when he suggested that you listen to your body.
At about 30, or 35 years old, I worked in a similar environment as you do, and I did an extended fast while working, with no problems.
After day 5 I had so much energy that after work I came home and ran 2 to to 3 miles at a 7 minute mile pace.
Don't dwell on what problems you might encounter, just do what feels right for you at the time. If working is a problem, you can always back off, ,or end the fast.