In brief: One in three teenage girls is on a diet—often a dangerous crash diet. When they enter adolescence, some girls stop playing childhood games and become more sedentary, which can lead to obesity. In addition, adolescent girls are self-conscious about their appearance and want to maintain a slender figure. Exercise is an effective alternative to fad diets. A weight-loss goal of 1 to 2 lb per week is recommended for the mid- to late-adolescent. Weight stabilization is recommended for early adolescents.