I don't know that I buy the argument that fat people cost more. There may be some higher costs up front. But then they die sooner. Old age is the real black hole for health care costs. I've never seen an obese 90 year old.
That is a very good, valid, intelligent argument. With the shorter lifespan, perhaps the higher operations cost less than chronic care or medications would over several decades.
You would need to factor in the income taxes paid for the longer lifespan to get an accurate reflection, and probably discount the cash flows back to the present, but yeah ... that is a good point. (Because you could get into a situation where someone costs the system $[x] times more by living longer but they also paid $[y] more in federal, state, and local taxes over all those years, offsetting their costs to some degree.) It would take some time and a roomful of PhD's to do the calculations but it would be interesting to find out the answer!