Abnormal eating customs that involve too much or too little food intake can be called eating disorders. There are two types of eating disorders: bulimia nervosa and anorexia nervosa. Although the causes are not fully comprehended, studies show  that eating disorders affect 3.5 percent of women, and 2 percent of men in the United States.Research cannot say, for certain, the cause of eating disorders, but it does indicate that they are likely caused by a combination of psychological, biological and environmental factors.

There can be a genetic potentiality for eating disorders. Biochemical causes can be low serotonin levels, norepinephrine abnormality, an infection, or the presence of a tumor. Psychological stress, such as that caused by puberty, can also trigger eating disorders and influence eating behaviors. Environmental causes can be abuse, parental influence, and social isolation, as well as cultural pressure that creates a distorted body image.

Bulimia Nervosa is an eating disorder that involves eating unusually large amounts of food, frequently and repeatedly, known as binge eating. Binging is followed by a period of purging, or compensative behavior, which involves the use of laxatives or diuretics, vomiting, and excessive exercise. Bulimia Nervosa behavior is usually done secretly, and Bulimics often experience shame following both bingeing and purging.

The bingeing and purging behaviors can be repeated as often as daily. Many Bulimics suffer from psychological problems like depression, substance abuse, or anxiety. Long term bulimia creates symptoms such as an aching and chronically inflamed throat, kidney problems, dehydration (caused by purging of fluids), swollen glands in the neck, and/or eventual irritation and intestinal pain from laxative abuse. Stomach acid washing over the teeth can also cause accelerated tooth decay.

Eating disorders can be present in another form, Anorexia Nervosa. This kind of eating disorder is recognized by symptoms such as excessive thinness, dehydration, dry skin, slowed pulse and breathing, low blood pressure, and weakness. The cause may be the will to maintain an unhealthy weight, coming from a misconception of body image. The constant fear of gaining weight, and a distorted body image, in which one always sees themselves as overweight, can be the primary reasons for this kind of eating disorder.

Most anorexics lose weight through extreme diets and/or excessive exercise, others use vomiting and laxatives. Anorexics weigh themselves very often and portion their food carefully. Studies reveal that anorexics have fluid and electrolyte imbalances that can lead to illness and death. Like Bulimia Nervosa, people with anorexia have psychological problems like anxiety, depression, substance abuse, and obsessive behavior.

Eating disorders can be treated as any other disease. Depending on the individual and the extent and seriousness of his or her disorder, different approaches to treatment may be recommended. Usually, those with severe and long-term anorexia must be hospitalized. Anorexics can end up doing irreparable damage to their kidneys and other organs.

Here are some common treatments for both Anorexia and Bulimia: CBT (Cognitive Behavioral Therapy) works on changing learned behaviors and the thoughts and beliefs that cause those behaviors; Dialectical  Behavior Therapy (developed by Linehan, Marsha M.); family therapy; interpersonal psychotherapy; art therapy; nutrition counseling; medical nutrition therapy; self help groups.