The average lifespan a person of a given age can expect, based on current mortality rates in the population. Life expectancy at birth is the most commonly quoted figure and serves as a broad indicator of a population’s health, reflecting nutrition, sanitation, healthcare, and living conditions. Diet influences life expectancy substantially: populations with balanced diets, healthy weights, and low rates of diet-related disease live longer on average. The measure is used by governments, insurers, and pension planners. While genetics play a role, public-health research consistently shows that improvements in nutrition and food safety have driven much of the historical rise in life expectancy.