Fat content in homemade stock
See Stock vs Broth - What&#39;s the difference in usage?

Like most cooking words there is no global definition. Fat content varies by ingredients and recipe. Some fat is retained in suspension, and some will be chemically attracted to components of the stock and be difficult to remove

Some people stir in the fat, most people skim it off

Commercial stock may have been centrifuged to get the fat content down to zero. This is not that practical to do at home, but can be done