Anorexia nervosa can damage nearly every organ system in the body. The prolonged starvation it causes forces the body to slow down, break down its own tissues for fuel, and shut off functions it deems nonessential for survival. The consequences range from a shrinking heart muscle to brittle bones, disrupted digestion, suppressed immune function, and a significantly elevated risk of death. Eating disorders carry the second highest mortality rate of any psychiatric illness, behind only opiate addiction.
Heart and Circulatory Damage
The heart is a muscle, and like every other muscle in the body, it shrinks when it’s starved. This loss of heart muscle mass causes the heart to beat more slowly, a condition called bradycardia, where resting heart rate drops below 60 beats per minute. Blood pressure also falls. Together, these changes mean less oxygen reaches the brain and extremities, which is why people with anorexia often feel dizzy, cold, and exhausted.
Anorexia can also trigger abnormal heart rhythms. One increasingly recognized complication is postural orthostatic tachycardia syndrome (POTS), which happens when the volume of blood returning to the heart drops too low upon standing. The heart compensates by racing, and the person feels lightheaded, dizzy, or faint. Cardiac complications are among the leading medical causes of death in anorexia.
Bone Loss That May Not Fully Reverse
Starvation disrupts the hormones responsible for building and maintaining bone. Estrogen, testosterone, and growth-related hormones all decline, and the body’s stress hormone (cortisol) often rises. The net effect is that bones lose density at a rate far beyond what’s normal for a person’s age. Studies show that 20% to 30% of people with anorexia develop osteoporosis, while 50% to 90% have at least some measurable bone thinning.
This matters because bone lost during anorexia, especially during adolescence when bones are still developing, may never fully recover even after weight restoration. The combination of reduced bone-building activity and increased bone breakdown creates a deficit that leaves people vulnerable to fractures for years. Low levels of a key growth factor that stimulates bone-forming cells appear to be a central driver of this process.
Digestive Slowdown
The digestive system essentially powers down during prolonged food restriction. The body reduces its production of digestive enzymes, and the muscles that move food through the stomach and intestines weaken from disuse. The result is gastroparesis, or delayed stomach emptying, which is nearly universal in malnourished patients. Research has found that food can take almost twice as long to leave the stomach compared to healthy individuals.
The same slowing affects the colon, leading to chronic constipation. These symptoms create a painful cycle: eating causes bloating, nausea, and discomfort, which reinforces the urge to restrict food further. The good news is that the digestive system does recover with sustained nutritional rehabilitation, but without it, these problems persist.
Reproductive and Hormonal Disruption
The body treats reproduction as nonessential during starvation and suppresses the hormones that drive it. In women and girls, this causes periods to stop entirely. Research indicates that menstruation typically resumes once weight reaches about 92% of the expected weight for a person’s height, and roughly 83% of people studied had regained their periods at follow-up. Fertility is unlikely to be permanently affected if weight is fully restored, though prolonged amenorrhea during adolescence can delay development and contribute to the bone loss described above.
Weakened Immune System and Blood Changes
Severe malnutrition damages the bone marrow, where blood cells are produced. The marrow’s fat stores, which provide the structural support blood cell production depends on, waste away along with fat everywhere else in the body. This leads to measurably lower counts across all three major blood cell types.
White blood cells, the body’s infection fighters, are hit hardest. Over half of people with the restrictive subtype of anorexia have white blood cell counts below normal range, which compromises the immune system and makes infections harder to fight off. About 16% to 20% develop anemia, leaving them fatigued and short of breath. A smaller percentage develop low platelet counts, which can impair blood clotting. The extent of marrow damage correlates directly with how much weight a person has lost.
Skin, Hair, and Nail Changes
Two distinctive changes happen to hair during anorexia. The first is hair loss from the scalp: without adequate protein and nutrients, the body shifts hair follicles into a resting phase, and hair falls out in greater quantities than normal. The second is the growth of lanugo, a fine, downy hair that appears on the face, arms, and back. While its exact purpose isn’t fully understood, lanugo is thought to be the body’s attempt to insulate itself as it loses the fat layer that normally retains heat. Brittle, splitting nails are also common.
Depression, Anxiety, and OCD
Anorexia rarely exists in isolation. Over a lifetime, up to 64% of people with anorexia experience major depression, up to 72% develop at least one anxiety disorder, and up to 62% meet criteria for obsessive-compulsive disorder. In one study of 177 patients, about a third had generalized anxiety and a third had social phobia.
These conditions aren’t just coincidental. Starvation itself changes brain chemistry in ways that worsen mood, increase rigidity of thinking, and heighten anxiety. At the same time, the presence of depression or anxiety makes the eating disorder more clinically severe: patients with comorbid depression are hospitalized more frequently, report worse quality of life, and score higher on measures of disordered eating. Suicide is one of the leading causes of death among people diagnosed with an eating disorder.
Dangers of Refeeding
One of the cruelest aspects of anorexia is that recovery itself carries medical risk. When a severely malnourished person begins eating again, the body’s demand for key minerals surges as cells start metabolizing food. Phosphorus, potassium, and magnesium rush from the bloodstream into cells, and because reserves are already depleted, blood levels of these minerals can plummet dangerously. This is called refeeding syndrome, and it typically occurs within the first five days of nutritional rehabilitation.
Phosphorus deficiency is the hallmark of refeeding syndrome and can cause muscle weakness, confusion, seizures, and heart failure if not carefully managed. This is why nutritional recovery from severe anorexia requires medical supervision, with gradual increases in calorie intake and close monitoring of blood chemistry.