Who has the greatest water, protein, and calorie needs per unit of body weight?

The 6-month-old infant has the greatest water, protein, and calorie needs per unit of body weight. During the early stages of life, particularly within the first year, infants experience rapid growth and development. This period demands a significant amount of nutrients, as their bodies are growing and developing vital organs and systems.

Water needs are particularly high in infants due to their larger surface area relative to their body weight, which can lead to greater fluid loss. Additionally, protein is essential for the growth of muscle and tissue, and infants require a higher protein intake relative to their body weight compared to older children and adolescents. Their caloric needs are also elevated as they require energy not only for growth but also for basic metabolic functions.

While a 1-month-old infant also has high needs, the 6-month-old infant typically requires even more due to increased growth rates and possibly the introduction of complementary foods, which can further raise their calorie, protein, and nutrient intake needs. In contrast, toddlers and adolescents, while they certainly require adequate nutrition for growth and development, have lower nutrient needs per unit of body weight compared to infants. Thus, the need for water, protein, and calories is most pronounced in the 6-month-old infant.