Fluid restriction in anorexia nervosa: a neglected symptom or new phenomenon?

The deliberate restriction of fluids to control weight is even more dangerous than food restriction since it results in several serious medical complications. However, there has been scant attention given to the anorexia nervosa patient's manipulation of fluids. It is our clinical impression that fluid restriction in this illness is more common than previously thought.

We summarize the demographic and clinical features of six cases of anorexia nervosa and one case of eating disorder not otherwise specified (ED-NOS) (subthreshold anorexia nervosa), where fluid restriction was a major behavioral problem. We then describe two of the anorexia nervosa cases in more detail. All were treated at a dieting disorders unit affiliated with the University of Sydney. Their preadmission history, psychological and physical status on admission, results of physical investigations, the beginning of the fluid restriction, fluid and food intake throughout treatment, and the resolution of the fluid restriction were assessed.

Patterns emerged in the relationship between eating and drinking. In all cases, food restriction was severe prior to the onset of fluid restriction but, notably, fluid intake recommenced prior to food intake. The reasons given by patients for restricting fluid were that it contained calories and that it made them feel full. Most anorexic patients equate feeling full with "feeling fat." Furthermore, they feel fully in control when they restrict fluid as well as food and this produces a strong motivation to maintain the behavior.

The cases illustrate the insidious nature and serious consequences of fluid restriction and the difficulties managing dieting-disordered patients who undertake it. Careful attention must be given to assessment and clinicians should be aware of fluid restriction as an important aspect of anorexic behavior.