Calorie Restriction for Longevity, abbreviated CRL, is a dietary philosophy proposing that eating substantially fewer calories while maintaining full nutrient intake can extend lifespan. The idea grew from animal studies in which restricted rodents and primates lived longer and stayed healthier, showing delayed age-related disease. Human evidence is limited to short-term trials showing improved metabolic markers, and the regimen demands meticulous planning to avoid malnutrition, loss of muscle, and hormonal disruption. Critics note the quality-of-life costs and unknown long-term effects in people. It remains a research interest rather than a recommended lifestyle, distinct from ordinary weight-loss dieting.