I think we are dealing with this exact same thing. My 4 yo will barely eat anything for days then he doesn't stop. Yesterday he basically ate non-stop from 7:30 am to 11:30 am, Cereal, banana, breakfast sausages, oatmeal, fruit, spaghetti - there's more, I just don't recall all of it. Then he took about a 2-2.5 hr break and started up again about 2:30 - pretzels, pears, almonds, granola bar, hamburger, a full plate of veggies, chicken nuggets, another pear...
Additionally, yesterday at about 10:45 am he had a complete meltdown, throwing toys, yelling, etc. When he calmed and I asked what was going on, why he'd thrown his toys, he said he didn't know. Then said he was hungry...so he had lunch at 11 am....
I don't know that I have any advice, but I can definitely commiserate. Oh, and both my boys can eat more in one meal than I do most of the day.
Right now we're focusing on smart snacks and keeping his blood sugar from getting too low. I'm wondering if this is also leading to some of the behavior issues we're seeing at school lately.
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DS - Adopted by loving parents 1995
DS1 7/2009 ('Stachio)
DS2 9/2011 (Peanut)