Due to start working long-ish days. Nervous!

[BlackButterfly23]

I've been working PT since finishing maternity leave, 9am-3pm three days a week.
I'm starting a new job for 3 days a week working 9.30am-6.30pm, which is nothing out of the ordinary but as I've not done full days like that for a while I'm really nervous about it.
I suffer from migraines which are usually triggered by stress and low blood sugar so that's what's worrying me as it will take me a while to adjust to the long periods between eating etc.
Is it unreasonable to explain to the new job about the migraines and ask if I can carry a small snack with me to try to avoid triggering one?
I know these days are not actually long and are just a standard work day and I know I'll be fine doing it once I settle into it as I used to work longer hours than that full time before having DC. Just the thought of the crippling migraines that are going to come from the first few weeks is making me nervous.

What kind of job is it? I work desk jobs and have never asked permission to eat snacks, I just do

It's a job in a nursery. I get an hour lunch break which is great and more than I get in my current job but it's more towards the end of the day that I know I'll start getting a migraine. I'm usually alright after a few weeks once my bodies adjusted and the stress of a new job has settled down.

If you know it's going to be a problem and has such a simple solution, I'd mention it.

Definitely say you need to keep your blood sugar up to prevent migraines. Just tell them all you need to do is have a quick snack in the afternoon. It will be fine. Good luck in your new job