Anorexia nervosa is an eating disorder characterized by severe restriction of food intake, a low body weight, and an intense fear of gaining weight. This restrictive behavior leads to malnutrition, which forces the body to prioritize essential functions over non-essential processes. Hair loss is a recognized and common physical manifestation of this internal struggle, often serving as a visible indicator that the body is operating under significant physiological stress. The body’s response to chronic starvation redirects resources away from systems like hair growth to conserve energy for vital organs, resulting in noticeable thinning and shedding.
The Underlying Causes of Hair Thinning
Hair loss in Anorexia Nervosa (AN) stems directly from the body’s state of resource depletion. Hair is primarily made of keratin, a protein, and severe protein deficiency immediately halts the production of new hair shafts. This lack of protein means the body cannot construct the building blocks necessary for robust hair growth, leading to brittle strands prone to breakage.
Micronutrient deficiencies further compound this problem, disrupting the normal hair growth cycle. Low iron levels can lead to anemia, reducing the oxygen supply available to hair follicles. Zinc scarcity also weakens the hair structure, as it is involved in enzymatic reactions within the follicle.
The chronic energy deficit causes a metabolic slowdown as the body attempts to conserve calories. This survival mechanism shuts down non-essential functions, placing hair growth on hold. The trauma of AN also causes a sustained release of stress hormones, particularly cortisol. Elevated cortisol levels disrupt the synchronized cycles of hair growth, prematurely signaling follicles to stop growing and begin shedding.
Understanding Telogen Effluvium
The specific type of hair shedding seen in AN is known as Telogen Effluvium (TE), a common response to physiological stress. TE is defined by the premature shift of growing hairs from the active Anagen phase into the resting Telogen phase. In a healthy scalp, only 10 to 15% of hairs are in the Telogen phase, but a severe stressor can force 30% or more into this resting stage.
A key characteristic of TE is the delay between the stressful event and the onset of hair loss. Shedding typically begins two to three months after the period of severe nutritional or metabolic stress. The resulting hair loss presents as a generalized thinning across the entire scalp, rather than distinct, localized bald patches.
Other Physical Signs of Anorexia Nervosa
Hair loss is one of many visible symptoms signaling the body is in a state of starvation. Many individuals with AN develop lanugo, a fine, downy layer of soft body hair on the face, back, and arms. This growth is the body’s attempt to insulate itself and conserve heat in response to the severe loss of subcutaneous fat.
The hormonal disruption caused by malnutrition often results in amenorrhea, the cessation of menstrual periods in women. The body suppresses reproductive functions because it lacks the energy reserves to support a pregnancy. Other common physical signs include extreme cold intolerance and persistent low body temperature. Brittle nails and extremely dry, discolored skin are frequent observations, as the body redirects resources away from these non-essential tissues. Severe fatigue and pronounced muscle wasting are also common, reflecting the body breaking down muscle tissue for fuel.
Hair Regrowth During Nutritional Recovery
Hair loss caused by AN is typically reversible once the underlying nutritional deficits are addressed. Regrowth is a common outcome once a patient commits to nutritional rehabilitation and weight restoration. The body must first exit survival mode before it will allocate energy to hair production again.
The process of seeing significant hair improvement is slow, requiring patience due to the hair growth cycle. Since follicles must restart the Anagen phase, it often takes six to twelve months of consistent, adequate nutrition to observe substantial regrowth. Treating the underlying eating disorder is the only effective solution. Once the body consistently receives a balanced diet rich in proteins and micronutrients, the hair cycle will normalize and gradually restore density.