Frailty is a dynamic, multidimensional state of diminished physiologic reserve that increases vulnerability to stressors and predicts disability, hospitalization, and mortality in older adults. Nutrition is one of the six pillars of lifestyle medicine (alongside physical activity, restorative sleep, stress management, positive social connection, and avoidance of risky substances), an evidence-based framework for promoting health and preventing disease. In older adults, optimal energy, protein, and micronutrient intake supports muscle mass, functional capacity, and metabolic and cognitive resilience, whereas poor diet quality and undernutrition worsen sleep, stress physiology, and frailty trajectories. This mini-review synthesizes how nutrition interacts with each pillar of lifestyle medicine in older adults and considers implications for clinical practice and research. Nutrition emerges as a central determinant of healthy aging, directly influencing physiologic resilience and shaping the benefits of the other lifestyle medicine pillars in preserving strength, function, and independence.