Our brains are 60% fat, and need lipids to function correctly.
It is my belief that this low fat diet fad, is the cause of rising numbers of anxiety, depression, and other mental problems.
Healthy fats from fish/meat/poultry avocado's nut's and coconut oil. Not corn,soy or the other low omega 3 vegetable oils.
However if you require focus/attention for a special occasion say like an examination nothing beats 24 hour fasting for sharpening our minds.