While many people struggle to lose weight, many others have difficulty gaining weight. The reason for difficulty gaining weight can sometimes come from genetics, lifestyle habits, or even medical problems.

Anorexia nervosa is a condition that involves excessive weight loss, mainly affecting women, and can cause serious damage to the physical and mental health of the sufferer.

Mental stress, psychological instability or mental illness such as depression can suppress hunger, causing nausea and poor digestion of food called anorexia nervosa. Treatment of anorexia nervosa is mainly through forms of psychotherapy.