The exact cause of eating disorders is not known. Perhaps part of the explanation for their prevalence in economically developed nations may be media messages regarding ideals of beauty and attractiveness. These messages often promote thinness as the female ideal. In order to be thin or slender, some people strive to maintain a weight that may not be healthy for their bodies. In some cases, though, it is possible to be slender and healthy at the same time. However, it becomes a serious health problem when people use detrimental methods (e.g., starvation) to achieve the desired results.

Generally, a combination of various factors may contribute to the development of eating disorders. These include:

• Gender. Females are more likely to develop eating disorders than males. One reason females may be at greater risk for developing eating disorders is their tendency to go on strict diets to achieve the “ideal” thin figure, which is often promoted by the media. According to a 2005 Youth At Risk Behavior Survey, 61 percent of adolescent girls are trying to lose weight and 32 percent believe they are overweight.However, eating disorders do occur in males. According to the U.S. National Institute of Mental Health (NIMH), an estimated 5 to 15 percent of people with anorexia nervosa or bulimia nervosa and approximately 35 percent of those with binge eating disorder are male.
  
  
• Age. Even though eating disorders may occur at any age, they are much more common among teenagers and young adults (people in their 20s and early 30s).
  
  
• Heredity. Eating disorders are more common among people with close family members with eating disorders. Current also research indicates that there are significant genetic contributions to the development of eating disorders.
  
  
• Mental illnesses. Oftentimes, people with eating disorders have other types of psychological illnesses including depression, anxiety disorders (e.g., obsessive-compulsive disorder) and substance abuse. The presence of a pre-existing emotional disorder often reinforces the eating disorder and vice versa.
  
  
• Low self-esteem and feelings of inadequacy or lack of control in life.
  
  
• Stress. Eating disorders also may be triggered by stressful situations and/or traumatic events including a history of abuse (e.g., physical, sexual), dysfunctional family, divorce, death of a family member or friend or starting a new school or job.
  
  
• Family and social influences. Individuals whose parents, siblings or other close family members and friends are overly critical of their weight, appearance and/or eating habits may be at increased risk of using harmful methods for weight control (e.g., purging) that can lead to the development of an eating disorder.
  
  
• Competitive sports and performance arts. People, especially females, who participate in highly competitive athletic activities (e.g., ballet, gymnastics) or work in the entertainment industry (e.g., actors, models) may be at greater risk of using harmful methods (e.g., starvation, abusing diet pills) for weight control due to the strict weight requirements of certain sports or performance arts. Prolonged use of such methods can put individuals at risk of developing eating disorders. 

In addition, recent studies indicate that some patients with eating disorders may have imbalances in chemicals in the brain that control, hunger, appetite and digestion. However, further research is necessary before the exact meaning and implications of these imbalances in regards to eating disorders can be established.