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
Low-calorie diet prevents age-related molecular changesMedical Xpress - 25-May-2018
Epigenetic changes strongly influence the way the genes operate.
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%.
Reduced-?calorie diet slows ageing in peopleNature - 22-Mar-2018
CALERIE multi-centre trial tested 200 healthy, non-obese adults over 2 years.