Obesity and poor physical fitness are major health care concerns for children. These conditions are associated with future insulin resistance, type 2 diabetes mellitus, lipid abnormalities, and hypertension. The combination of increased caloric intake and decreased physical activity causes obesity in children. Addressing caloric intake and food selection alone may not resolve the underlying issues of insulin resistance and poor cardiac fitness. In adults, the leading predictor of cardiovascular and all-cause mortality is the level of physical fitness and not weight status. Because most adults do not perform moderate exercise 30 minutes per day on most days of the week as recommended, establishing healthy habits in children is important to reach this physical fitness goal.

Various behavioral interventions in childhood have had mixed results. In a recent study, a school-based exercise program for adolescent girls resulted in an increase in physical activity and prevented the decline in cardiovascular fitness normally seen in this age group. Carrel and colleagues evaluated the effectiveness of a school-based fitness program on body composition, cardiovascular fitness level, and insulin sensitivity in overweight children.

Children from one middle school whose body mass indexes (BMIs) were above the 95th percentile for their ages were invited to participate in the study. Before the intervention and at the end of the nine-month school year, data on height, weight, fasting blood glucose and insulin levels, body composition, and cardiovascular fitness were obtained by physical examination. After the baseline data were collected, the children were assigned randomly to the intervention or standard gym classes. Fifty-three students agreed to participate in the study, with 27 assigned to the intervention group.

Students in the intervention group received a small nutrition education component that included information on healthy eating habits. The intervention group was divided into small classes (12 to 14 students) to allow for increased instructor attention, more opportunity for motivation, and less time standing in line. The curriculum was personalized to better match the students' skills. During the class, lifestyle-focused activities such as walking, cycling, and snowshoeing were emphasized. In the standard gym class, the children participated in more traditional sports. The main outcome measures were cardiovascular fitness, fasting insulin and glucose levels, and body composition.

At baseline, the groups were similar with regard to age, BMI, percentage of body fat, lean body mass, and maximum oxygen consumption. The intervention group had a significantly greater loss of body fat (–4.1 percent) compared with the standard gym class group. They also had a significantly greater increase in cardiovascular fitness compared with the standard gym class. Fasting insulin levels decreased by 5.1 μIU per mL (35.4 pmol per L) in the intervention group, compared with an increase of 3.0 μIU per mL (20.8 pmol per L) in the control group. No one in the intervention group dropped out, whereas three students dropped out of the control group for reasons unrelated to the study.

The authors conclude that a fitness-oriented, school-based intervention can have a positive effect on body composition, cardiovascular fitness, and fasting insulin levels in overweight children. The authors add that, as part of the public health approach to improving the health of overweight children, partnering with school districts is an important component of any intervention.