FACT: the only scientifically proven and agreed upon method to increase lifespan among any type of mammal is calorie restriction.
I'm proposing that all this talk about Vegan, Vegetarian, Paleo diet, Keto diet, Carnivore diet, High Fat diet, Low Carb diet, no Fat diet, etc... boils down to a few simple facts when it comes to living longer.
FACT: The longest living people in the world are mostly plant based eaters from Japan followed by vegans from Loma Linda California; traditional Japanese eat meet 1 - 2 times a month. See Dr. Greger "40 year old vegan dies of heart attached " , vegan versus meat eater life span video where meat eaters win.
There are people eating nothing but meat and people eating nothing but plants, both claiming superior health.
The Life Span Theory
What if the reason plant based eaters usually live longer is calorie and nutrient restriction. In other words they are eating a normal amount of calories but the human body cannot take them in, most of the nutrients and caloric content pass through unused. Since the human body cannot extract most the nutrients from plant based material (ie. fiber), these plant eaters are effectively on a nutrient and calorie restricted diet; as in the first fact stated in this writing. Remember it's not what you eat it''s what you absorb.
Could this be why the plant eaters are living longer?