This paper was a great read. It is quite a bit more wholesome than just talking about the health- and longevity-benefits of CR but it clearly mentions them and contains a great graph about the correlation of BMI to health-care cost, that you cannot really find anywhere else as most studies don't even include people below a BMI of 20.
This one does! It starts at a BMI of 13 and we can finally see what the real healthy BMI-range is:
It is 17-20 with the sweet-spot being at 18!