Dehydration: This is a common issue in patients with anorexia or restrictive eating patterns, leading to headaches due to insufficient fluid intake and electrolyte imbalances.

Electrolyte Imbalance: Patients with anorexia or restrictive eating may have inadequate intake of essential electrolytes like sodium, potassium, and magnesium, which can cause headaches.
Nutritional Deficiencies: Deficiencies in vitamins and minerals such as vitamin B12, iron, or magnesium can lead to headaches in individuals with restrictive eating patterns.
Anxiety or Depression: These conditions are common comorbidities with eating disorders and can cause or exacerbate headaches.
Hypoglycemia: Inadequate food intake can lead to low blood sugar, which may cause headaches among other symptoms.

Pituitary Apoplexy: Although rare, this condition involves bleeding into the pituitary gland and can be associated with severe headaches. It's a medical emergency that requires immediate attention.
Subarachnoid Hemorrhage: A life-threatening condition that can cause sudden, severe headaches. While not directly related to anorexia, it's crucial to consider in the differential diagnosis of headaches to avoid missing a potentially fatal condition.
Meningitis or Encephalitis: Infections that can cause severe headaches and are medical emergencies. Patients with compromised immune systems due to malnutrition may be at higher risk.

Pseudotumor Cerebri (Idiopathic Intracranial Hypertension): This condition involves increased pressure within the skull without a detectable cause and can lead to headaches. It's more common in individuals with significant weight fluctuations.
Cerebral Vasculitis: Inflammation of the blood vessels in the brain, which can cause headaches among other neurological symptoms. It's rare and would be considered if other diagnoses are ruled out and there are additional suggestive symptoms.