Default File Display is Using Incorrect Image Style
After some search, I got your issue and from where you can set that. So I delete my previous answer and following is the updated one.

As in my setting, I have four Image settings,


Default
Teaser
Preview
Wysiwig


Now, by default it is taking some height and width. 

Now those all four setting you can change at Admin/Structure/File types/Images/Manage file Display and you can find all four image file set on right hand top corner in following images. Now, you can see as I have selected Default and at bottom of the page it is showing None(original image).


  


Note: Now, image uploaded in the body field area before save/post of the body content may not show what you have selected, but if you post it it will show what you image style you had selected. As stated in following image.