Lowering BMI Improves Insulin Sensitivity in Teens

A new study involving Children’s Hospital investigators found obese teenagers who reduced their body mass index (BMI) by 8 percent or more had improvements in insulin sensitivity, an important metabolic factor related to the later development of type 2 diabetes. To achieve the reduction in BMI, the teens followed a family-based, lifestyle-modification weight loss program that offers the potential to become a broader model.

“This threshold effect that occurs at 8 percent suggests that obese adolescents don’t need to lose enormous amounts of weight to achieve improvements,” said pediatric endocrinologist Lorraine Levitt Katz, MD of Children’s Hospital’s Diabetes Center for Children. The findings were published recently in The Journal of Pediatrics.

The investigators analyzed results in 113 primarily urban adolescents, aged 13 to 17, of whom 81 percent were female and 62 percent were African American. At the start of the study, their mean BMI was 37.1, placing them in the severely obese range. None had type 2 diabetes, but their obesity placed them at high risk for developing the disease in the future.

An important goal of the study was to determine the threshold of weight loss that significantly impacted insulin sensitivity, glucose tolerance, and the presence of metabolic syndrome (MS). MS, as well as abnormal values in insulin sensitivity and glucose tolerance, is associated with the development of type 2 diabetes. In type 2 diabetes, the body is unable to produce enough or properly use insulin. Improved insulin sensitivity reflects a better ability to process insulin.

The main finding of the current study was a significant improvement in all measures of insulin sensitivity. There was also a trend toward improvement in metabolic syndrome.

The weight loss program used family-based lifestyle modification. Clinicians taught the teens about healthful eating habits and encouraged them to increase physical activities, such as walking, climbing stairs, and engaging in sports.

“This study reinforces the importance of behavior change — adopting healthy eating habits and getting more physical activity — in achieving weight loss in adolescents,” added Dr. Berkowitz, the director of CHOP’s Weight and Eating Disorders Research Program.