Adolescence and older adulthood can be both enjoyable and challenging life stages. Adolescents are at risk of iron-deficiency anemia and eating disorders, whereas older adults are at risk of malnutrition, urinary tract infections, and chronic disease. Diet and sedentary activities can influence weight status. The long-term implications of having an unhealthy weight status are likely to persist into adulthood, increasing the risk of chronic diseases such as heart disease and type 2 diabetes. Therefore, establishing healthy lifestyle choices and habits such as a healthy diet and physical activity during the formative years of childhood and adolescence is essential for long-term health and well-being in adulthood. Many contributing factors affect one’s lifestyle choices, including social (family and peer influences, cultural influences, and financial constraints) and environmental (the availability of healthy food options, safety, and security conditions) factors. However, public health initiatives can address some of these factors by promoting healthy eating habits and physical activity, implementing policies that support healthy environments, and facilitating educational programming. This chapter provides an overview of the common nutritional problems during adolescence and older adulthood and the nutritional requirements of both life stages. Additionally, strategies and resources that can help adolescents and older adults develop healthy eating habits are discussed.