Reduction in BMI Improves Insulin Selectivity in Obese Teens

Obese teenagers who reduced their BMI by 8% or more had improvements in insulin sensitivity, an important metabolic factor related to the later development of type 2 diabetes. The teens followed a family-based, lifestyle-modification weight loss program that offers the potential to become a broader model. The findings appeared online on in The Journal of Pediatrics. .

“This threshold effect that occurs at 8% suggests that obese adolescents don’t need to lose enormous amounts of weight to achieve improvements,” says pediatric endocrinologist Lorraine Levitt Katz, MD, of the Diabetes Center for Children at The Children’s Hospital of Philadelphia. “The improvements in insulin sensitivity occurred after four months of participating in a lifestyle-modification program.”

The study team analyzed results in 113 primarily urban adolescents, aged 13 to 17, of whom 81% were female, and 62% 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 to develop 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. 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 threshold of 8%—the level at which a decreased BMI showed improved insulin sensitivity—was consistent with results found previously in adults. Importantly, says first author Pamela Abrams, MD, a member of the study team while at Children’s Hospital, and currently at St. Luke’s Center for Diabetes and Endocrinology, “while the ideal goal is to achieve normal weight levels, you don’t need to be skinny to see improvements. This 8% reduction in BMI is achievable, and BMI is easy for primary care physicians to track.”

The weight loss program used family-based lifestyle modification, explained coauthor and Children’s Hospital psychiatrist Robert I. Berkowitz, MD, the principal investigator of a federally sponsored clinical trial of weight loss treatments, from which the researchers analyzed data for the current study. Clinicians taught the teens and adults about healthful eating habits and encouraged them to increase physical activities, such as walking, climbing stairs, and engaging in sports. Some of the teens used portion-controlled, prepackaged foods, while others ate regular food but followed a calorie-restricted, nutritionally balanced diet.

The teens attended weekly group counseling meetings, separately from the parents, who had their own weekly group meetings. Group leaders encouraged parents to model healthful behavior for their children, and to support the teens’ behavior changes. “This study reinforces the importance of behavior change—adopting healthy eating habits and getting more physical activity—in achieving weight loss in adolescents,” adds Berkowitz.

The authors added that this study was relatively small, and that future research in larger numbers of patients is needed to reveal longer-term results, and to investigate further effects on adolescent metabolism and health. “These are preliminary results,” says Katz, “but this is the first study to identify a threshold effect for these improvements, and later studies can build on this one. Having more evidence about reasonable weight loss goals will help researchers develop more effective programs for teenage patients.”

Source: Children's Hospital of Philadelphia

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