Calorie Restriction
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.
Resources
More info: CR Society International
Recent News
Relative Energy Deficiency in Sport caused by under-eating
BBC - 09-Dec-2018Athletes starving themselves causes hormone and bone problems
Read more...Low-calorie diet prevents age-related molecular changes
Medical Xpress - 25-May-2018Short-term diets may accelerate the manifestation of aging symptoms
Read more...CR Leads to Longer Life but Less Grey Matter
Genetic Engineering & Biotechnology News (GEN) - 05-Apr-2018New study shows caloric restriction in lemurs extended lifespan up to 50%.
Read more...