I doubt there are any Irish people
that old around anymore

)
I'm pretty sure there were more than three meals, since even in modern Ireland some families would have 4 meals (breakfast, lunch, dinner, supper).
You also have to remember that potatoes were pretty much all Irish people had to eat in those days. A quick google search tells me the average person today eats ~6.5 lbs of food a day. Given that farmers are doing manual labour all day and potatoes aren't that nutritious, it's not too difficult to imagine.