By default in WordPress if you create a new post, or custom post type based on post, and fill in the title but no body and press “Publish” it will save it as a draft instead of actually publishing it. If the post is saved as a draft it won’t show up in your list of posts during the loop.
Can you elaborate more on why you’re trying to accomplish this? There might be an easier solution for the bigger goal.
However, if you do want it to work exactly as specified, you’ll To specifically modify which posts go through the loop, you would need to run a custom query.
Did you already modify the loop by adding parameters or doing a custom query? If so, please post that for a start.