How can not eating enough affect your mental health?

Food is critical....: The brain, center of cognition & mental health well being, needs food in form of protein and carbohydrates and liquid in order to function optimally. Without food there are both physiological and psychological issues that occur. Even in treatment of eating disorders, until there is a minimal weight the patient will not be treated because of impact of starvation on brain, mental health f'ing

Eat for health: Severely inadequate nutrition could cause all sorts of mental health problems, including depression, anxiety, or even delirium. At milder levels, inadequate blood sugar causes decreases in "willpower" or self control. To be at one's best mentally requires being at one's best nutritionally.