An 18-month Trial of a Low Glycemic Load Diet

The prevalence of obesity has risen dramatically among children in the U.S. since the 1960s. Effective treatment of childhood obesity is widely recognized as instrumental to public health efforts to combat type 2 diabetes and heart disease. Evidence from animal studies, short-term human studies and epidemiology suggests that diets designed to minimize the rise in postprandial blood glucose, that is low glycemic index, may be useful in the treatment of obesity and related complications. This project proposes an month RCT comparing a low glycemic load diet to a conventional low fat diet. Both diet groups will receive identical treatment intensity, behavioral modification and physical activity recommendations. The primary endpoint will be change in percent body fat by dexa-scan at 18 months; other outcomes include insulin resistance and CVD risk factors. Compliance will be assessed by interviewer-administered, 24-hour dietary recalls.

Inclusion criteria

• Age 18 to 35 years
• Body mass index (BMI) ≥ 30 kg/m2
• Access to a working telephone
• Conversant in English
• Written medical clearance from a primary care physician or nurse practitioner, ruling out any pre-existing or complicating medical condition

Exclusion criteria

• Body weight >300 lbs
• Major medical illness (heart, kidney or liver disease; diabetes; cancer; endocrinopathy; psychiatric illness) or other active medical problem
• An obesity-associated genetic syndrome (e.g., Prader-Willi)
• An abnormal screening laboratory test (ALT, creatinine, BUN, hematocrit)
• Fasting blood glucose ≥ 126 mg/dl)
• Taking any prescription medication that affects body weight (glucocorticoids, neuropsychiatric agents), blood pressure, or serum cholesterol concentrations
• Currently smoking (1 cigarette during any of the last 7 days)
• Previous diagnosis of an eating disorder (anorexia nervosa, bulimia, binge-eating disorder)
• If female, not pregnant or planning to become pregnant in the next 18 months and not lactating
• Failure to complete the pre-enrollment visits