This is the basic calculation that the HSFC wants us to make:
This includes getting 150 minutes per week of moderate to vigorous exercise, which the foundation said can reduce the risk of heart disease, stroke, high blood pressure and diabetes by 30 per cent. On the other hand, inactivity can shave four years off a person's lifespan, it said.
On the surface this looks like a good deal. Working out 150 minutes a week from the age of 20 and 80 amounts to a little less of a year in total and for that you get an extra 4 years of life. If only my other investments could match such a return.
Of course the 4 years claim is likely based on actuary data which means that it is an average over the general population. For you as an individual the results are far more variable than the claim would have you believe. After all there are other factors at work besides exercising. Genetics and other environmental factors play an important role. It is possible that you work out religiously from a young age and still die of a heart disease at the age of 50.
Furthermore there are a lot of other things you can die of. You don’t get any return on your investment if you get hit by a car and break your neck.
I don’t say this to imply that exercise is not worth the time or effort. I merely point out that the long term benefits might not be worth the time or effort (personally I put greater stock in the short term benefits of exercise). It probably is worth it but we should understand that there is what economists call a knowledge problem; as an individual I don’t know how beneficial exercise will be for me.
This is important to keep in mind because too often governments make policies on the misguided notion that encouraging people to exercise would be universally beneficial. Governments should allow individuals to make their own choices and take their own risks.