Can eating a gluten-free diet help prevent or delay the onset of celiac disease?

Not exactly : If you have celiac disease, then a gluten-free diet will help delay the onset of symptoms from it. However, if you do not have celiac to begin with, eating a gluten-free diet will make no difference whatsoever. It will not prevent celiac disease. If you feel you may have celiac, due to how you feel when you eat gluten, you should see a gastroenterologist to sort it out. Good luck.