It doesn't count what the impact of extracting gasoline is, or the effect of transporting it on a supertanker. And what about feeding all those people working in the oil industry? and the energy used by lobbyists to convince people to drill in Alaska. And aren't they eating meat themselves? And the BP leak? How much km of cycling did that cost? This kind of study is completely bogus.
Not to mention whether exercise is substituted. What about a driver who runs on a treadmill, or does some equivalent amount of exercise without getting transportation in return?
Plus, did I miss something, or was food not counted as a renewable resource? While agriculture is not carbon neutral, it's also not a 100% carbon source.
There's an argument to be made that people who are healthier throughout their lives will be able to have a higher quality of life, and need less care, well into old age. So even if they live longer it might not cost as much in old age care. But you're right that that's more of a gut-feeling/heuristic kind of thing. We'd need actual numbers to know for sure.
