Anorexia nervosa affects nearly every organ system in the body, from the heart and brain to the bones and skin. The damage begins early, intensifies with time, and carries a mortality risk roughly 2.5 times higher than that of the general population. Some effects reverse with weight restoration, while others, particularly bone loss, can persist for years or become permanent.
Heart Rate Drops and Muscle Thinning
The cardiovascular system is one of the first to show measurable damage. Bradycardia, a resting heart rate below 60 beats per minute, is the most common heart rhythm abnormality in anorexia. In one clinical review, 36% of all eating disorder patients had heart rates in this range, with some dropping as low as 43 bpm. Blood pressure also falls, sometimes to readings like 99/60 mmHg while lying down.
These changes aren’t just the body “slowing down.” The heart itself physically shrinks. Echocardiography studies have found a 30 to 50% reduction in the mass of the left ventricle, the chamber responsible for pumping blood to the rest of the body. That reduction is disproportionate to overall weight loss, meaning the heart muscle wastes away faster than other tissues. Some patients also develop small fluid collections around the heart (pericardial effusions), though these typically resolve within three months of refeeding. The good news: heart rate and blood pressure often improve quickly with even mild weight gain. In one documented case, a patient’s heart rate rose from 43 to 62 bpm after just four weeks of inpatient treatment.
The Brain Physically Shrinks
Starvation reduces the volume of gray matter in the brain, particularly in the frontal lobes and the insula, a region deep in the brain involved in body awareness and emotional processing. These aren’t random losses. The frontal lobes control planning, decision-making, self-control, and working memory. The insula helps you interpret internal body signals like hunger, fullness, and pain. When these areas shrink, the cognitive and emotional symptoms of anorexia can intensify: rigid thinking, difficulty reading social cues, poor body image, and trouble making decisions about food or anything else.
Other affected regions include the parietal cortex, which plays a role in body image perception, and the amygdala, which processes anxiety. This means the illness physically reshapes the brain in ways that reinforce the very thoughts and behaviors driving it. Research on recovery suggests that some gray matter volume returns with weight restoration, though the timeline and completeness of that recovery vary.
Bone Loss That May Not Fully Reverse
Decreased bone mineral density is one of the most serious long-term complications of anorexia. The mechanism is layered. Estrogen normally acts as a brake on bone breakdown by suppressing the cells that dissolve bone tissue. When estrogen drops, as it does when menstruation stops, bone loss accelerates. Testosterone plays a similar protective role and also declines during starvation. But hormonal changes alone don’t explain the full picture.
Nutritional factors are equally important. Bone formation markers track closely with BMI, body fat percentage, and levels of a growth hormone called IGF-1. This means the body can’t build new bone without adequate fuel, regardless of hormone levels. Interestingly, bone density improvements during recovery often begin before menstruation returns, and estrogen replacement therapy alone doesn’t prevent bone loss in anorexia patients. This confirms that nutritional rehabilitation, not just hormonal correction, is essential. Even so, bone density may never fully return to normal, especially after prolonged illness, leaving some people with lasting fracture risk.
The Digestive System Slows Down
One of the most frustrating physical effects of anorexia is delayed gastric emptying. The stomach loses its ability to move food through at a normal pace, causing nausea, vomiting, bloating, and an overwhelming sense of fullness after eating very little. In one study, 78% of anorexia patients reported upper gastrointestinal symptoms before refeeding, and delayed emptying of solid food was confirmed in 71% of cases. Liquid emptying was delayed in 64%.
This creates a vicious cycle: eating feels physically uncomfortable, which reinforces the avoidance of food. The condition improves with consistent nutrition, and the stomach can return to normal function without medication. But the process takes time and often requires psychological support alongside nutritional rehabilitation, because the discomfort during early recovery is real and significant.
Metabolism Drops Beyond What Weight Loss Explains
The body responds to chronic starvation by aggressively cutting energy expenditure. In one study, resting energy expenditure in women with anorexia averaged 854 calories per day, compared to 1,080 calories predicted for their body size. That’s a gap of about 226 calories per day that can’t be explained by simply being smaller. The body actively suppresses cellular metabolism to conserve energy, saving an estimated 150 to 250 additional calories daily beyond what reduced body mass accounts for.
Thyroid function plays a central role. Levels of T3, the active thyroid hormone that regulates metabolic rate, drop significantly during starvation. The result is a body running on minimal power: low body temperature, constant cold, fatigue, and sluggish organ function across the board. This metabolic suppression is one reason people with anorexia feel cold all the time and why the body grows lanugo hair as compensation.
Skin, Hair, and Nail Changes
Fine, downy hair called lanugo often appears on the face, arms, and back during severe malnutrition. This is the body’s attempt to insulate itself when subcutaneous fat is depleted, similar to how mammals grow thicker fur in cold conditions. It’s a visible sign that the body is struggling to maintain its core temperature.
Skin becomes dry and flaky as essential fatty acids needed to maintain the skin’s lipid barrier run low. Iron and B vitamin deficiencies cause a pale, sallow complexion through anemia. Nails grow brittle, weak, and prone to splitting due to zinc and biotin deficiency. Hair on the scalp becomes dry, dull, and breaks easily. These changes generally improve with nutritional rehabilitation, though hair regrowth can take months.
Blood Cell Counts Fall
About one-third of people with anorexia develop anemia and a low white blood cell count. The bone marrow, which produces blood cells, becomes suppressed during prolonged malnutrition. Red blood cell reduction leads to fatigue, weakness, and dizziness. Low white blood cells, particularly a type called neutrophils, weaken the immune system and increase vulnerability to infections. Platelet counts can also drop, though this is less common. These blood count abnormalities typically improve with weight restoration as bone marrow function recovers.
Long-Term Mortality Risk
Anorexia carries serious long-term risks even after acute medical stabilization. In a study following women for 29 years, those with a history of anorexia died at a rate of 3.24 per 1,000 person-years compared to 0.38 for women without anorexia. The elevated risk of death persisted up to 20 years after hospitalization.
The leading causes of death may surprise people who associate anorexia primarily with heart problems. While cardiovascular complications dominate during acute illness, the long-term mortality picture looks different. The strongest associations were with diabetes and endocrine disease (7.6 times the risk), pneumonia (8.2 times the risk), and suicide (4.9 times the risk). Liver and digestive disease, as well as organ failure, also carried significantly elevated risk. Pneumonia risk likely reflects the immune suppression caused by chronic malnutrition, while the diabetes association may stem from lasting damage to metabolic and endocrine function.
The Danger of Refeeding
Recovery itself carries physical risks if not managed carefully. Refeeding syndrome occurs when a malnourished body suddenly receives nutrition again. During prolonged starvation, minerals like phosphorus, potassium, and magnesium become severely depleted inside cells. When food is reintroduced, insulin surges and drives these already-scarce minerals from the bloodstream into cells, causing dangerous drops in blood levels.
The hallmark of refeeding syndrome is a sharp fall in phosphorus, but potassium and magnesium also plummet. These minerals are critical for heart rhythm, muscle function, and breathing. The syndrome can also cause fluid retention, abnormal sodium balance, and thiamine (vitamin B1) deficiency. Refeeding syndrome is potentially fatal, which is why nutritional rehabilitation after severe anorexia typically begins with carefully controlled calorie increases under medical supervision rather than unrestricted eating.