[Closed] Nutrition Q

Periodically I have sessions (both work & non work related) where I end up doing stupid long hours (18+/day), getting a little bit of poor sleep/doze, repeat for 4 or 5 days. The work is often short periods of intense physical activity, followed by several hours of stooging around "on duty" where I need to be alert and with it, but not actually doing anything physical. So overall I'm not burning that many calories

There's usually 2 or 3 proper meals a day (usually high carb content) provided plus constant access to snacky/shite sugary food lying around - haribo, chocolate, biscuits, crisps etc + endless coffee. I get quite strange if I have too much coffee, so I tend to end up grazing on the junk food, which works, as it provides a constant sugar burn, but means I'm consuming far more calories than I'm burning, and by the end of a week of it, I'm feeling very blobby (and my guts are in uproar!).

So the question is what should I be eating to maintain the concentration, without taking on excess calories. Bear in mind I'm usually away from home, often isolated, and starting and finishing at strange hours, so don't necessarily have access to "proper" shops. Plus, once I get off duty, all I want to do is sleep.

I eat most things, but I don't do fish or bananas.

Thoughts?

Thanks...