"Yes, I eat lunch."
Translation:Ja, ik eet middageten.
No, it isn't. "Middageten" is the main meal, eaten at noon. In a time when nearly everybody would normally eat the main meal at noon, no word was needed to indicate specifically that this was the main meal. "Lunch" was borrowed from English to indicate a meal at noon that is not the main meal. Nowadays, that's the norm, but Dutch never got around to a word of its own for that specific type of meal.
I would like to add to that adjust that.
I agree with lunch you wouldn't be referring to the main meal (usually). However middageten doesn't háve to mean the main meal.
Ik heb nog geen middageten gehad. Simply means I haven't had lunch yet. I haven't eaten since breakfast. I didn't eat yet this afternoon.