Taking your nutrition in smaller, more frequent servings is actually ideal. Don't get hung up on the numbers as much as you should pay attention to how you feel. It's never bad to eat (favorable) food when you're hungry. It is a far worse thing to force yourself to wait, stomach growling, until it's "time" to eat. Best way to avoid the glucose roller coaster is to eat small, frequent servings.
[A tip from personal experience: If you have a supervisor or boss who won't allow eating at your work station, tell him you are borderline hypoglycemic or diabetic (you won't be lying). If he still doesn't like it, threaten to sue him for not catering to your particular situation. If that doesn't work, get a better job. It's your health.]
You will know best if you drop out of the Zone, and remember it is necessary to pay attention to how you feel throughout the day, keep a mental diary of eating habits that were effective, the foods that kept hunger away for 5 hours, the foods that didn't make you sleepy, etc.
I have found, for instance, that I can remain 'Zoned' when I eat 2-block snacks while at work, with a frequency of every 2 or 3 hours.
Bring Zone-favorable food to work that you can snack on in small increments, (cheese, deli meat, tuna, nuts, fruit, salad). Make your "lunch" a 2-block helping, and have a couple snacks before and after. Enjoy your morning and afternoon snacks while your unhealthy colleagues take their cigarettes breaks. The shorter lunch will allow you to take a walk or read a book while the fat ladies bask under the flourescent light of the lunchroom, eat their pasta salads and french fries, and share tips they heard from their sister-in-law, or on Oprah, about the latest miracle diet fad they're gonna hafta try [i:22bb9a3a22]next[/i:22bb9a3a22] week.
Hallowe'en temptations? I keep plenty of honey peanut Balance bars handy when the ol' Reese's bowl starts calling.