How do you extend human life by 40 years using a process that destroys LBM while low LBM has been shown to massively decrease the survival rate of both cancer and CVD, the biggest killer diseases that exist? To increase longevity, you need to increase chronic disease survival rates. To do that you need to increase LBM. That means RT and high protein should be top of the list.
As for 40 years life extension, an effect like that would be bigger than the negative effects of tobacco, an effect like that would long have shown up in the epi data by now. Look at epi data from any country that went through a great famine. If autophagy was to increase human lifespan, famine should be a good thing for the survivors, right? Well, guess what, even decades after famines end, mortality numbers amongst the survivors continue to be higher than those of comparable populations that were affected less by the famine.
A low LBM is a higher risk factor for chronic disease mortality than obesity. It's not quite up there yet with smoking, but its closer than any dietary factor. The best defense against low LBM happens to be resistance training combined with a diet that is high in proteins. High protein might be easiest to achieve with animal-sourced foods, it is perfectly possible using just plant-based sources as well. Protein won't help you live to a hundred twenty years old, it will help you to stay mobile into old age and it will help you survive longer if you happen to have the bad luck of getting cancer or CVD. Each of these factors could add months or even years to your life expectancy.
RE: Where do you get your protein?