This is the 1344th most frequent Japanese word.
どんどん
Rapidly; steadily; progressively; one after another.
In this sentence, "どんどん" indicates a steady and rapid progression or increase.
進捗がどんどん進んでいます。
The progress is advancing rapidly.
Here, "どんどん" conveys encouragement to proceed continuously and without holding back.
どんどん話してください。
Please keep talking without hesitation.
In this usage, "どんどん" suggests that the action of eating should proceed energetically and abundantly.