Having an eating disorder such as anorexia nervosa can increase your risk of developing osteoporosis. Read on to find out more about the mechanisms by which anorexia can affect your bones, and what can be done to reverse it.
Anorexia nervosa is an eating disorder and serious mental health condition. People with anorexia often have a distorted view of their bodies, and so try to control their body weight by restricting the amount of food they eat, or over-exercising, or both.¹ These extreme efforts to lose weight can significantly interfere with their lives.
Anorexia is most common in young women, with average age of onset around 16, but as many as 1 in 4 people with an eating disorder are men.²
Not eating enough can lead to malnutrition, where the diet does not contain the right nutrients to keep you healthy. Chronic malnutrition, such as in anorexia, can lead to severe health problems.
Patients with anorexia increase their risk of osteoporosis by up to 40%.³
We build 80% of our bone density between the ages of 9 and 15.⁴ Peak bone mass is regarded as a key determinant of osteoporosis and fracture risk later in adulthood.⁵ Those who develop anorexia before the age of 18 have been shown to have significantly lower bone density than those who develop the disease in adulthood*.⁶
Long-term risk is more apparent in females. Adolescent boys typically go through multiple growth spurts, whereas girls only have one chance to boost their skeletal health in a singular growth spurt.⁷ Unfortunately, this time overlaps with the years when eating disorders are most prevalent.
*This isn’t to say that those who develop anorexia in adulthood aren’t also at risk of osteoporosis. With continued low weight, adults with anorexia lose an average of 2.5% of their bone density per year, putting them at high risk of developing osteopenia and subsequent osteoporosis. But on restoration of healthy weight, bone density tends to regain faster than those who developed anorexia in adolescence.⁸
The mechanisms underlying bone density loss in anorexia are complex, but research shows that oestrogen, IGF-1 and cortisol all play an important role.
When you’re not fueling yourself with enough food, your body conserves energy by shutting off any ‘non-essential’ physiological processes. One of these processes is oestrogen production.
A symptom of this in people with eating disorders is the disappearance of menstrual periods, also known as amenorrhea.
Oestrogen plays a critical role in bone metabolism, exerting many protective effects on bone. Without it, bone-building cells, or osteoblasts, are not able to function. Oestrogen also acts to limit the rate at which cells that break down bone, or osteoclasts, can function.⁹
This is why the menopause, which causes a rapid decrease in oestrogen levels, is a big risk factor for osteoporosis.
Read more on the link between hormones and osteoporosis here.
IGF-1, insulin-like growth factor 1, is another nutritionally-dependent hormone associated with low bone mass.
Chronic starvation can lead to growth hormone resistance. This comes as a result of adaptive measures to conserve energy, similar to the drop in oestrogen production – there is less focus on reproduction and growth in order for the body to survive.
Growth hormone usually stimulates release of IGF-1 from the pituitary gland, but with resistance this process is greatly reduced.IGF-1 usually encourages osteoblast growth, promoting bone formation. Many researchers have linked low levels of IGF-1 with low bone density in both postmenopausal women and those with anorexia.¹⁰
Periods of starvation can put your body under stress, triggering the release of cortisol.¹¹
Cortisol levels in the body can linger for a long time, and have a negative impact on your health, particularly on your bones.
Elevated cortisol levels can meddle with osteoblast formation and accelerate action of osteoclasts. More bone tissue is broken down than rebuilt, which can dramatically decrease bone density.¹² Patients with chronically elevated levels of cortisol, such as in anorexia, can therefore be at increased risk of osteoporosis.
Poor nutrition, particularly lack of protein intake, can lead to decreased muscle mass.
Weakened muscles can lead to bone instability, and increased risk of falling and fractures due to poor balance.¹³
Muscle and bone metabolism are very closely linked; muscle loss can induce bone loss and vice versa – studies show that decreased muscle mass directly suppresses new bone formation, and increases resorption of bone into the blood.¹⁴ Poor bone density can in turn contribute to further muscle loss.¹⁵
Anorexia is a very complex medical condition that can take years to recover from fully. The longer you have anorexia, the more your bone health is likely to suffer.
It is essential to seek help and start treatment for anorexia as early as possible. Treating the disorder directly is the most important thing you can do for your overall health and wellbeing.
Research shows that rebuilding of bone is possible with the right lifestyle interventions, even in people with severe bone loss. In some cases, problems can be completely reversed.¹⁶
If you or anyone you know is struggling with an eating disorder, you may find these organisations helpful: