Which lifestyle habit is most likely to reduce resting oxygen saturation?

Smoking is identified as the lifestyle habit most likely to reduce resting oxygen saturation. This is primarily due to the inhalation of harmful substances that decrease oxygen-carrying capacity in the blood. Smoking introduces carbon monoxide and other toxins into the lungs, impairing the ability of red blood cells to transport oxygen effectively. In addition to these immediate effects, smoking can also lead to chronic respiratory problems, such as chronic obstructive pulmonary disease (COPD) and emphysema, which further contribute to lower oxygen saturation levels.

In contrast, regular exercise promotes enhanced lung capacity and efficiency in oxygen utilization, ultimately improving resting oxygen saturation. A healthy diet supports overall health and can positively affect respiratory function, while adequate hydration is crucial for maintaining optimal physiological functions, including circulation and oxygen transport. Therefore, smoking stands out as the primary cause for a reduction in resting oxygen saturation among the lifestyle options provided.