Final answer:
Susan needs to improve her body composition by engaging in regular physical activity.
Step-by-step explanation:
Susan's situation relates to her body composition, which is a measure of the proportion of fat, muscle, and other tissues in her body.
Continuously sitting for long periods can lead to a sedentary lifestyle and weight gain, primarily due to reduced energy expenditure and lower muscle mass.
To improve her body composition, Susan could engage in regular physical activity, including both cardiovascular exercises (such as walking, running, or cycling) and strength training exercises (such as weightlifting or resistance band workouts).