Implications of Growth as a Time-Specific Event

Nutritional influences on human growth are commonly assessed as weight or length/height outcomes, and adequacy is determined by reference to population-based growth charts. These approaches estimate gross effects only and are insensitive proxies for the dynamic processes by which nutritional components affect tissue accrual. Weight provides information about calorie balance and/or hydration status, while offering little insight into functional physiology. Height is often attributed meaning in accordance with growth charts, a static group level statistical summary unrelated to individual skeletal dynamics. Evidence accumulates that the lifelong health consequences of early growth necessitate a better understanding of individual-level body composition and its developmental determinants. Empirical evidence documents that children's skeletal and head circumference growth occurs in time-specific saltations separated by intervals of no growth. These saltation events are accompanied by discrete increases and decreases in subcutaneous fat implying pulsatile metabolic changes that may or may not be reflected in weight. The mechanisms determining the timing of these saltatory growth events to emerge from stasis, as well as the required energy and chemical building blocks to fuel and support them, remain to be clarified. Their occurrence suggests that the present understanding of nutritional needs for growth is incomplete.