What is a common health risk associated with being underweight?

Being underweight can lead to several health risks, and one significant concern is the loss of bone density. This occurs because individuals who are underweight may not be consuming adequate nutrients, particularly calcium and vitamin D, which are vital for maintaining healthy bones. Low body weight can also contribute to decreased estrogen levels in women, which is important for bone health. As a result, this may increase the risk of osteoporosis and fractures over time.

While increased muscle mass and improved immunity would generally be associated with a healthy body weight or being overweight, they are not typically benefits of being underweight. Additionally, while it's true that being underweight can put individuals at a higher risk of some chronic diseases, bone density loss is specifically a direct consequence of being underweight. Hence, the focus on bone density loss as a risk is more prominent in this context.