Anorexia nervosa (AN) is a severe eating disorder defined by the restriction of energy intake, leading to a significantly low body weight, coupled with an intense fear of gaining weight or becoming fat. While the primary focus often rests on the reduction of food consumption, the control and manipulation of fluid intake is an often overlooked aspect of the disorder. Individuals with AN frequently apply the same rigid control mechanisms to water as they do to calories. This manipulation of hydration status can have profound medical consequences, often surpassing the dangers posed by food restriction alone.
The Complex Relationship with Fluid Intake
The question of whether individuals with anorexia drink water is complex, as their behavior is highly varied and often paradoxical. Many people with AN severely restrict their fluid intake, sometimes to the point of near-total abstinence, to avoid the sensation of fullness. They often equate a full stomach with “feeling fat,” which motivates further restriction. This deliberate dehydration extends control from solid food to all liquids, including water.
Conversely, some individuals consume excessive amounts of water, known as water loading or polydipsia, which is also a form of manipulation. This behavior is sometimes used as a substitute for food, creating a temporary feeling of satiation to mask intense hunger. Excessive water intake is also frequently linked to purging behaviors, consumed in massive volumes to induce vomiting. Both severe restriction and extreme over-consumption are driven by the underlying pathology of the eating disorder.
Fluid Manipulation and Weight Distortion
Fluid manipulation is often directly connected to the fear of weight gain and the desire to influence the number displayed on a scale. Many individuals restrict fluids in the hours or days leading up to a scheduled medical weigh-in to artificially lower their body weight. By avoiding liquids, they attempt to minimize “water weight” and achieve a temporary, desirable number on the scale. This tactic feeds into the disorder’s need for control and achievement.
In a contrasting strategy, some resort to rapid, excessive water loading immediately before a weigh-in. The goal is often to temporarily inflate the weight to evade detection of severe weight loss or to meet a minimum weight requirement set by treatment teams. Consuming large volumes, such as four to six liters in a short timeframe, can overwhelm the body’s normal fluid regulation capacity. This control over hydration reflects the psychological toll of the disorder, where the fear of the scale dictates basic biological functions.
Severe Physiological Consequences of Dehydration
The manipulation of fluid intake, whether through restriction or excess, creates severe medical dangers, particularly through the disruption of electrolyte balance. Electrolytes, such as sodium and potassium, regulate nerve and muscle function, fluid balance, and heart rhythm. Extreme water restriction or fluid loss through purging can lead to hypokalemia, a low level of potassium, which causes muscle weakness and irregular heartbeats that may lead to sudden cardiac death.
Conversely, excessive water loading can lead to hyponatremia, where the blood sodium level drops below 135 mmol/L due to dilution. Severe hyponatremia can cause brain swelling, seizures, confusion, and coma. Chronic dehydration from fluid restriction puts immense strain on the kidneys, forcing them to conserve water. This stress can culminate in acute kidney injury or chronic renal failure, especially when combined with malnutrition.
Dehydration also affects the cardiovascular system, contributing to orthostatic hypotension, a sudden drop in blood pressure upon standing. This low blood volume can cause dizziness, lightheadedness, and fainting, increasing the risk of falls and injury. Medical professionals treating AN must carefully assess and monitor hydration status through blood tests and vital signs. Safe and supervised rehydration is an immediate step necessary to stabilize the patient and prevent fatal physiological disruptions.