It is abundantly obvious that reality lies somewhere in the middle ground. You are a completely different being every 7 months. With the exception of oxygen, all the replacing atoms come from what we eat and drink. Imagine what this says about 7 months worth of fast food. Let's start with beverages.
Water is our most prominent chemical and most rapidly replaced chemical.
We use it in all our metabolic activity. Unfortunately there is a tendency to lace this vital fluid with a plethora of less desirable substances. Some contain up to 240 calories per 8-ounce serving. We can get our supply of carbohydrates in the foods we eat. We don't need them repeated in our beverages.