The only proven way of currently extending life expectancy in a variety of mammals is undernourishment (not malnourishment) but requires further study to see whether it has undesirable side effects.
Long lived species have less response to famine so, according to Aubrey de Grey, not likely to have a big impact in humans.
More info: CR Society International
Relative Energy Deficiency in Sport caused by under-eatingBBC - 09-Dec-2018
Athletes starving themselves causes hormone and bone problems
Low-calorie diet prevents age-related molecular changesMedical Xpress - 25-May-2018
Short-term diets may accelerate the manifestation of aging symptoms
CR Leads to Longer Life but Less Grey MatterGenetic Engineering & Biotechnology News (GEN) - 05-Apr-2018
New study shows caloric restriction in lemurs extended lifespan up to 50%.