Final answer:
Aside from 'lucent hair', all options (hair loss, lackluster hair, unhealthy scalp) can result from the inadequate nutrient intake associated with crash dieting and anorexia nervosa. Hair loss and lackluster hair are notably due to protein deficiency and subsequently weakened hair structure.
Step-by-step explanation:
All of the side effects listed, except for 'lucent hair', can indeed be a consequence of crash dieting and anorexia nervosa. 'Hair loss' and 'lackluster hair' are common symptoms due to the lack of protein and essential nutrients in the diet. When the body experiences a deficiency in protein, it conserves what it has for vital functions which can lead to these conditions. Hair is made up of proteins, specifically keratin, and when the body is deprived of protein, it can no longer maintain healthy hair growth, leading to hair loss and lackluster hair. Moreover, the hair becomes more prone to breakage due to the weakened disulfide bonds. The scalp can become 'unhealthy' as well, due to poor nutrition affecting the skin and other bodily systems. However, the term 'lucent hair' is not commonly used to describe a consequence of nutritional deficiencies or eating disorders.