Nutritional needs during adolescence are influenced mainly by the onset of puberty with its associated increased growth rate and changes in body composition and organ systems. After age 11, girls accrue approximately 12 percent of their adult stature and 36 percent of adult weight, and boys approximately 20 percent of their adult stature and 50 percent of adult weight . Growth during adolescence is accompanied by an increased proportion of body fat for girls and an increased proportion of lean body mass and blood volume in boys . (See "Normal puberty".)
The recommended dietary energy requirements in adolescents are defined to maintain health, promote optimal growth and maturation, and support a desirable level of physical activity. Dietary energy recommendations must be accompanied by strong encouragement for physical activity compatible with health, prevention of obesity, and adequate social and psychologic development.
The recommended dietary energy requirements in adolescents are reviewed here. Dietary requirements for other nutrients in adolescents are discussed separately. (See "Dietary history and recommended dietary intake in children" and "Calcium requirements in adolescents" and "Iron requirements and iron deficiency in adolescents".)
Basal metabolism is the energy expended for cellular and tissue processes that maintain life. It is measured under standard conditions of thermoneutrality, immobility, and fasting. The basal metabolic rate (BMR) relative to weight increases from birth to two years and then gradually declines through adolescence (figure 1) .
The effect of age on BMR is a function of changes in body composition through childhood and adolescence. BMR is strongly correlated with the fat free mass (FFM) that comprises the bulk of the active metabolic tissue. The marked sex differences in intensity and duration of the adolescent growth spurt and in the proportion of FFM dictate the energy and nutrient needs of boys and girls. The World Health Organization (WHO) has endorsed the Schofield equations for the estimation of BMR that take into account sex, age, and body weight [3,4].