I think the response to this questions depends on why you are doing an elimination diet. But to truly determine how foods affect you, keep as many factors the same as you can while changing one thing at a time. Alternatively, should you choose to follow more of a whole30 style diet that eliminates more than 1 thing, be sure to add one thing back in at a time. Wait 3 days before adding in another food. This allows you to begin to uncover how certain foods might impact how you feel.