Learn Dutch: Met een goede eetlust heb je altijd trek. - With a good appetite you are always hungry.

Because the sentence starts with the prepositional phrase Met een goede eetlust. In Dutch, when you start a sentence with something other than the subject, the verb must still take the second position. This pushes the subject immediately after the verb, which is a rule known as inversion.

What is the difference between eetlust and trek?

Eetlust translates to "appetite" in a general, biological sense. Trek refers to an immediate feeling of hunger or a specific craving. The expression trek hebben is the most common, everyday way to say "to be hungry" in Dutch.

Why is je used here instead of the emphasized jij?

In this sentence, je acts as a generic pronoun meaning "one" or "people in general" (just like the generic "you" in English). If you used jij, it would sound like you are pointing out one specific person, which doesn't fit a general statement like this one.

Why does the adjective goede get an -e at the end?

The noun eetlust is a de-word (because its core part, lust, is de lust). When an adjective is placed directly in front of a de-word, it always receives an -e ending.