Paul is not saying that we should keep our bodies healthy and go to the gym because our bodies are the Temple of God, although we should keep ourselves healthy for many biblical reasons. The “you” here is plural, it is y’all in Southern vernacular. Paul is saying that we as the community of believers are the Temple of God. We are the stones that make up this “building” and how we choose.
1 Corinthians 3:10-17