## Core Concept
Anorexia nervosa is a psychological eating disorder characterized by an intense fear of gaining weight and a distorted body image, leading to restricted food intake and significant weight loss. It is more prevalent among females than males. The condition often begins during adolescence or early adulthood.

## Why the Correct Answer is Right
The correct answer, **D. Young females**, is right because anorexia nervosa predominantly affects young females, especially those in the adolescent and young adult age groups. This demographic is more susceptible due to a combination of genetic, psychological, and sociocultural factors. The disorder is associated with a fear of gaining weight, a desire to be thin, and a distorted perception of one's body shape.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because anorexia nervosa is not specifically highlighted as being common in middle-aged males, although it can occur in males of any age.
- **Option B:** This option is incorrect as there is no specific or highlighted increased prevalence of anorexia nervosa in elderly populations compared to younger populations.
- **Option C:** This option is incorrect because, while anorexia nervosa can affect individuals of various ages and backgrounds, it is notably more common in young females than in older males or the general population across all ages.

## Clinical Pearl / High-Yield Fact
A key point to remember is that early detection and intervention in anorexia nervosa significantly improve the chances of recovery. Clinicians should be vigilant for signs of the disorder, particularly in young female patients who present with significant weight loss, amenorrhea, or other symptoms suggestive of an eating disorder.

## Correct Answer: D. Young females.