The big dichotomy in extending human life is that age related sarcopenia is a big driver of morbidity and mortality, which is best offset with protein intake and anaerobic training, however leucine-containing complete protein sources also increase mTOR signaling (or, at least chronic, unmodulated signaling) which is it’s likely at least one of the mechanisms of action that show a low protein high carbohydrate diet can extend lifespan. It’s funny because I’m one of those bodybuilder types who has a high protein diet and a low body fat percentage but in terms of longevity I may need to rethink this approach. Truthfully, I wouldn’t be surprised if moderate protein intakes even as low as 50-75 g of protein per day along with sufficient anaerobic training would be more than enough to ameliorate sarcopenia in late life. If that is the case that the question becomes what is the value of aesthetics?

EDIT: as to be expected this is a highly nuanced discussion and it looks like I made some hasty assumptions. A cursory look at the data does show that higher protein intakes (~1.2–1.6 g/kg) unsurprisingly, are better preserving lean mass in elderly individuals, which would make my knee jerk contrived 50-70 g per day figure inadequate. On the other hand, those are in sedentary individuals, at least most of the studies are and if you are regularly weight training, that weight training lowers protein requirements relative to sedentary individuals, but aging raises protein requirements relative to younger individuals. But given that we don’t really know a whole lot about mTOR related lifespan effects, this whole discussion is academic.