The excessive vomiting that is associated with bulimia does not allow the body to absorb the potassium the way it should. Poor Diet. Poor diet can also cause potassium deficiency. Eating foods that are high in sodium can also cause a lack of potassium in the body.. When the body gets too much salt and not enough foods that are high in potassium, a deficiency can occur.hen the body is unable to absorb potassium or does not receive potassium in foods, the result is a potassium deficiency. Eating Disorders. One cause of a potassium deficiency is eating disorders. The two main eating disorders are anorexia and bulimia.