Anorexia Nervosa (AN) is a complex psychiatric disorder defined by extreme caloric restriction, low body weight, and an intense fear of gaining weight. This sustained state of severe malnutrition triggers a cascade of physiological and hormonal adaptations throughout the body. Since obesity and excess energy intake are established risk factors for many malignancies, the question arises whether the severe energy deficit characteristic of AN might reduce or increase the risk of developing cancer. This article examines the current scientific evidence to understand the relationship between this serious eating disorder and cancer risk.
Current Evidence on Overall Cancer Risk
Large-scale epidemiological studies examining the overall risk of cancer in individuals with AN suggest that the standardized incidence ratio (SIR) is generally neutral or only slightly reduced compared to the general population. A systematic review and meta-analysis involving over 42,000 participants found no statistically significant difference in the incidence of all cancers combined for women with AN, reporting a combined risk ratio of 0.97. This finding indicates that, despite severe and prolonged energy restriction, the overall probability of developing a malignancy is not substantially different from that of a healthy individual. This neutral finding is supported by a large-scale cohort study from Nordic countries, which also reported an incidence rate ratio of 0.97 for all cancer sites in women with AN. While animal models of energy restriction often show a dramatic reduction in tumor growth, this protective effect does not translate into a widespread cancer risk reduction in humans. The complexity of the disorder, involving not just low caloric intake but also vitamin and nutrient deficiencies, may explain why the expected protective effect is not universally observed.
How Chronic Malnutrition Affects Cellular Health
The state of chronic starvation forces the body into a catabolic state, redirecting resources to maintain life-sustaining functions. This profound metabolic shift can limit the proliferation of malignant cells, which require significant energy and resources to grow and divide. One proposed mechanism is the suppression of circulating growth factors, such as Insulin-like Growth Factor 1 (IGF-1), which normally promote cell growth and survival and are often implicated in cancer development.
However, chronic malnutrition also creates competing biological pressures that can undermine the body’s defenses against cancer. While cell growth is suppressed, the lack of proper nutrients and energy can compromise the immune system’s ability to recognize and destroy nascent cancer cells. Furthermore, the nutritional deficiencies associated with AN may impair DNA repair mechanisms, potentially allowing damaged cells to survive and accumulate mutations. This biological paradox—suppressed growth versus compromised defense—likely contributes to the observed neutral overall cancer risk, as the protective and detrimental effects may cancel each other out over time.
Specific Cancer Risks Linked to Hormonal Changes
The severe weight loss and malnutrition in AN disrupt the endocrine system, which affects the risk for specific hormone-sensitive cancers. Female patients often experience amenorrhea, signaling a state of hypogonadism and extremely low estrogen levels, essentially reverting the body to a prepubertal hormonal state. This results in a significantly reduced lifetime exposure to estrogen, a known driver of certain malignancies.
Consequently, studies consistently show a reduced risk for cancers sensitive to female sex hormones, particularly breast cancer, with a risk ratio estimated at approximately 0.60 compared to the general population. A reduced risk has also been observed for other female reproductive system cancers, such as endometrial and ovarian cancers, for similar hormonal reasons. Conversely, the disorder may be associated with an increased risk for cancers of the gastrointestinal tract, such as esophageal cancer. This increased risk is linked not to the malnutrition itself, but to disordered eating behaviors, like frequent vomiting, which can cause chronic irritation and damage to the esophageal lining.
Prioritizing Recovery for Long-Term Health
While the link between AN and overall cancer risk is complex and largely neutral, the disorder poses immediate risks to nearly every other major organ system. The long-term consequences of AN are severe, often leading to life-threatening complications unrelated to cancer. For instance, the heart muscle can atrophy, leading to dangerous conditions like bradycardia, hypotension, and other cardiac complications that are a major cause of death in severe cases. Bone health is also affected, with the loss of bone mineral density being a common and often permanent complication, resulting in osteopenia, osteoporosis, and a high risk of fractures. Furthermore, the brain can suffer from generalized atrophy, which may lead to persistent cognitive deficits and neurological issues. These non-cancer risks underscore that recovery from AN is paramount to mitigating the far more common and immediate threats to long-term health and survival.