Underweight or stalled growth (in children), weight fluctuations and malnutrition lead to electrolyte disorders, metabolic and endocrine changes. Somatic changes are secondary to starvation and long-term underweight and usually reversible once weight is restored to normal. Secondary amenorrhea is common and menstruation is often delayed in cases of prepubescent onset. Slow heartbeat, low blood pressure, hypothermia and dehydration are common. Skin, hair and tooth quality are all affected. Gastrointestinal issues are virtually always present and may subside once weight is restored to normal, but is overrepresented in follow-ups of AN cases treated at CAP.
Those who were overweight before their weight loss might have muscle weakness even when they have a surplus of body fat and normal BMI. Insufficient energy intake leads to a low level of anabolic hormones. A large part of initial weight gain is peripheral body fat and muscle mass only starts to normalise once the endocrine system has stabilised. Malnutrition and starvation-induced sex hormone deficit can lead to abnormal development of the brain. Deteriorated brain function is restored in most but not all cases upon recovery (in some cases it can be a primary deviance).
Severe starvation over several years can lead to heart failure, kidney failure and osteoporosis with fractures. Symptomatic vitamin deficiency occurs in cases of extreme long-term undernutrition. Excess mortality with regard to age is 6-10 percent and related to the eating disorder (infections, electrolyte balance disorder, complications of extreme undernutrition) but also suicide.
Differential diagnoses like hyper- and hypothyroidism, diabetes, gastrointestinal disease or tumour disease are usually not hard to differentiate from AN but may as concurrent diagnoses exacerbate the eating disorder or contribute to triggering eating disorder behaviour.