Which of the following factors is NOT affected by prolonged sitting?

Prolonged sitting is known to have several metabolic consequences that can directly influence insulin sensitivity, HDL levels, and triglyceride levels. Research indicates that reduced movement can lead to decreased insulin sensitivity, as the body's ability to respond effectively to insulin diminishes with long periods of inactivity. Similarly, prolonged sitting is associated with adverse effects on lipid profiles, leading to lower levels of HDL (the "good" cholesterol) and higher triglyceride levels, both of which are key factors in cardiovascular health.

In contrast, bone density is largely influenced by weight-bearing activities and mechanical loading on bones. While sedentary behavior can contribute to bone loss over time, it is not as directly impacted by periods of sitting as the metabolic parameters mentioned earlier. Therefore, prolonged sitting does not have the same immediate and pronounced effect on bone density as it does on the other factors listed, making it the correct choice in this context. Regular physical activity, particularly resistance and weight-bearing exercises, plays a crucial role in maintaining and improving bone density, highlighting the importance of movement over prolonged periods of inactivity.