Definitive article - in or out

Hola Stuart

Have a look at these two similar sentences:

"Me gusta comer pan" (I like eating bread- [in general])

"Me gusta comer (el) pan con un poco de mantequilla y mermelada." (I like eating bread with a bit of butter and jam.- [more specific])

On the second one where the speaker is being a bit more specific about how he/she likes eating bread, you can use the article or omit it. 

In the first one where the speaker is talking more in general, we don't use the article.

Here is another example with a different verb:

"Me encanta leer libros"

"Me encanta leer (los) libros que cuentan aventuras"

Hope it is useful

Saludos

Inma