Diet and depression: what you eat impacts your mood

Here’s another study that also finds this effect for the Mediterranean diet: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0791-y

Search for the SMILES acronym for related articles. The Mediterranean diet is also the most research supported diet for weight loss / improved health purposes. Olive oil seems to be a particularly important part of it.