Osteoporosis & Osteopenia from Eating Disorders

Anorexia nervosa can significantly affect bone health by causing malnutrition and hormonal imbalances, which reduce bone density and impair bone growth. Prolonged low body weight and poor nutrition can weaken bones and increase the risk of fractures and osteoporosis. Early intervention and addressing nutritional rehabilitation are crucial for minimizing bone damage.

Anorexia & Bone Loss

Many of the characteristic behaviors of eating disorders – food restriction, purging, bingeing and overexercising – impact bone health. Bone loss is most closely tied to anorexia nervosa, with 90% of patients with anorexia nervosa having low bone mineral density. While bone health issues are most common in patients with anorexia nervosa, orthopedic problems can also present in those with bulimia nervosa, avoidant restrictive food intake disorder (ARFID) and OSFED.

There are two forms of bone mineral loss:

• Osteopenia: a mild loss of bone mineral density.
• Osteoporosis: severe loss of bone mineral density.

Osteoporosis is one of the few complications that may persist even when patients are weight restored or medically stabilized.

How eating disorders impact bone health

One of the biggest factors influencing bone health is age of onset of an eating disorder. Those who develop an eating disorder at younger ages may experience more severe bone health issues than those who develop an eating disorder when they are older because they’re unable to reach peak bone mass.

In young people, new bone is created faster than old bone can be reabsorbed. Bone mass peaks in the late teens, after which bone production slows down but continues until around age 30 before it starts to shrink about 1% annually.

Endocrine abnormalities

In patients who are severely malnourished, endocrine abnormalities can cause bone production to decrease and bone reabsorption to increase, leading to low bone mineral density. Since bone mass peaks in the late teens, around or after the time eating disorders often develops in girls, many of these girls never reach peak bone mass and start their young adulthood with bones weaker than their peers, putting them at risk for:

• Fractures and broken bones
• Chronic pain associated with bone fractures
• Reduced strength and mobility
• Emotional suffering associated with a chronic illness or pain
• Shorter stature

Why osteopenia and osteoporosis occur

Low weight & lean muscle mass

Body weight and physical activity are important determinants of bone mineral density. Low weight and malnutrition cause changes in body composition, including a decreased lean muscle mass that negatively impacts bone mineral density. Bone growth occurs when muscle exerts forces on bone, but this effect is lost with reduced muscle mass.

Overexercising

Although exercise can be beneficial for bone health at a healthy weight, it has a negative effect on bone density when malnourished or amenorrheic (lack of a period). Research is limited in this regard but one study found that excessive exercise of moderate intensity resulted in further bone density loss in people with AN, which is likely mediated by estrogen deficiency.

Hormonal changes

There are multiple hormonal changes that develop with malnutrition that also negatively impact bone health but we will focus on a few below:

• Gonadal hormones, including estrogen and testosterone, are deficient in malnutrition, and both are critical for bone growth in adolescence and bone density maintenance in adults.
• Growth hormone is one of our major anabolic hormones produced by the pituitary gland within the brain. It has numerous functions including building up of bone, but is unable to do its job appropriately when an individual is malnourished.
• Cortisol, our major stress hormone, is up-regulated with malnutrition to help combat some of the physiologic and metabolic changes that accompany malnutrition. However, it also acts to break down bone and contributes to reduction in bone mineral density.
• Adipokines and gut hormones: Adipokines and gut hormones have numerous metabolic effects in the body, but also impact bone density. The changes to these hormone levels with malnutrition ultimately have a deleterious effect on bone density.

Medications

Some necessary medications used to treat the comorbid medical and psychiatric conditions seen with eating disorders can negatively impact bone disease and/or vitamin D metabolism, which is very important for bone density.

Testing for & treating low bone mineral density

Lab testing & imaging for osteoporosis

Early identification is crucial for treating and reversing bone loss. The best diagnostic tool for patients at high risk for bone loss is a DEXA (dual-energy x-ray absorptiometry) scan of the hip and lower spine. The DEXA scan can be helpful in formulating a comprehensive care plan to address any bone loss concerns and prevent further degradation. Various laboratory investigations can measure qualitative markers on bone health and may be abnormal even before radiologic changes are noticed. These can include C-telopeptide, alkaline phosphatase, osteopontin, and others; however, they are not routinely as part the daily clinical monitoring but are instead utilized more for research purposes.

Can osteoporosis be reversed?

Addressing the underlying eating disorder is essential in reversing osteoporosis and improving bone health. Medical stabilization, nutrition therapy (including refeeding) and eventual weight restoration are often the first steps in addressing osteoporosis and osteopenia for patients with severe eating disorders. Medications can also be utilized in certain situations to help improve bone density.

Low-impact and light exercise can also have benefits, but it’s important to ensure it doesn’t progress to compulsive or vigorous exercise. Walking, gardening and non-strenuous yoga can help under the guidance of an eating disorder specialist. Research suggests that supervised programs can help rebuild bone, even in those with severe bone loss.

References

• Anand, P., & Mehler, P. S. (2019). Osteoporosis recovery in severe anorexia nervosa: a case report. Journal of Eating Disorders, 7(1). https://doi.org/10.1186/s40337-019-0269-8
• Gibson, D., Watters, A., Cost, J., Mascolo, M., & Mehler, P. S. (2020). Extreme anorexia nervosa: medical findings, outcomes, and inferences from a retrospective cohort. Journal of Eating Disorders, 8(1).
• Grinspoon, S. et al. (2000) Prevalence and predictive factors for regional osteopenia in women with anorexia nervosa. Annals of internal medicine. 133 (10), 790–794.
• Steinman, J., & Shibli-Rahhal, A. (2019). Anorexia Nervosa and Osteoporosis: Pathophysiology and Treatment. Journal of Bone Metabolism, 26(3), 133.
• Waugh, E. J., Blake Woodside, D., Beaton, D. E., Cote, P, Hawker, G. A. (2011). Effects of exercise on bone mass in young women with anorexia nervosa. Med Sci Sports Exerc, 43(5), 755-63.
• Workman, C., Blalock, D. V., & Mehler, P. S. (2020). Bone density status in a large population of patients with anorexia nervosa. Bone, 131, 115161.