Junk food is linked to both moderate and severe psychological distress. The study revealed that California adults who consumed more unhealthy food were also more likely to report symptoms of either moderate or severe psychological distress than their peers who consume a healthier diet. Source 3h.
It's always about what you eat, not just for the physical reasons but for the mental too. Your mind also needs the essential vitamins and minerals as much as the body, so by filling yourself constantly with oil or loads of sugar..You'll end up shutting down before you even realize it.
After all, you are what you eat.