A 1991 calculation was made to determine what, if any, additional health-care costs beyond the ordinary are borne by society at large for people who live a sedentary life.
Conclusion (Thus)
People's voluntary choice not to exercise places a significant burden on society.
Evidence
If you voluntarily live a sedentary lifestyle, your additional health-care costs are about $1650 higher than someone without a sedentary lifestyle.
Evaluate
Given that ... someone living a sedentary lifestyle costs $1650 (on average) more in health care costs than does someone who lives a non-sedentary lifestyle,
How could we still argue that ... Choosing not to exercise is not placing a significant burden on society?
Maybe the health care costs of being sedentary are higher for society, but some other costs of sedentary lives are cheaper for society? That would help us argue that sedentary people are not significantly more expensive to society.
We could also just acknowledge that sedentary people are more expensive but argue that an extra $1650 over the course of a lifetime fails to qualify as a significant burden.
Goal
Look for some way to say that even though the health care costs are somewhat higher for a sedentary lifestyle, a sedentary lifestyle overall does not cost society a burdensome extra amount of money, compared to a non-sedentary lifestyle.