Nutritional needs fluctuate throughout life stages due to changes in metabolism, growth, and overall activity levels. During infancy, nutrition focuses on breast milk or formula to support rapid growth. Adolescents require additional calories and nutrients like calcium and iron for growth and development. For adults, balanced nutrition is crucial for maintaining weight and preventing chronic diseases. Older adults often require fewer calories but need more of certain nutrients like vitamin D and B12. Understanding these shifts helps individuals tailor their diets to better support their changing health needs.