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Joslin study shows dietary fat can affect glucose levels and insulin requirements in type 1 diabetes

Findings have major implications for insulin dosing and nutritional recommendations

Joslin Diabetes Center

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IMAGE: Howard Wolpert, M.D., leads clinical trials that help to analyze the best ways to adopt technology for type 1 diabetes management. He is an Investigator in the Section on Clinical,... view more

Credit: John Soares

BOSTON - March 27, 2013 - In a study of patients with type 1 diabetes, Joslin researchers found that dietary fat can affect glucose levels and insulin requirements. These findings, which appeared in the April edition of Diabetes Care, have major implications for the management of type 1 diabetes.

Research has shown that dietary fat and free fatty acids (FFAs) impair insulin sensitivity and increase glucose production. Most studies have focused on the role of fat in the development of type 2 diabetes. However, studies of people with type 1 diabetes have shown that higher-fat pizza meals cause hyperglycemia hours after being consumed.

In reviews of continuous glucose monitoring and food log data from adult patients with type 1 diabetes, Joslin clinicians observed that "several hours after eating high-fat meals, glucose levels went up," says study lead author Howard Wolpert, MD, Senior Physician in the Joslin Clinic Section on Adult Diabetes and the Director of the Insulin Pump Program at Joslin. "We wanted to determine the underlying cause of these unexplained fluctuations."

Seven participants (adults with type 1 diabetes with an average age of 55) successfully completed the study. They spent two days at Beth Israel Deaconess Medical Center eating carefully controlled meals and having their glucose and insulin levels monitored.

All breakfasts and lunches featured identical low-fat content. The two dinners had identical carbohydrate and protein content but one was low-fat and the other high-fat. For two 18-hour periods beginning before dinner, participants had their insulin automatically regulated by a closed-loop system and their glucose and plasma insulin levels tested at frequent intervals.

Study results showed that participants required more insulin after eating the high-fat dinner than the low-fat dinner (12.6 units compared to 9 units). In contrast, the two breakfast meals required similar insulin doses. Despite the increased insulin, participants had greater hyperglycemia after the high-fat dinner with insulin levels elevated five to ten hours after the meal. The average increase in insulin was 42 percent with significant individual differences.

"These findings highlight the limitations of basing mealtime insulin dosing for type 1 diabetes solely on carbohydrate intake," says Dr. Wolpert. "We need to consider fat as well as carbohydrates in insulin dosing calculations as well as in nutritional recommendations."

Dr. Wolpert and the research team are about to start a new study funded by the Juvenile Diabetes Research Foundation that aims to define optimal insulin dosages for higher-fat meals. Participants will eat controlled high-fat meals and receive increasingly higher doses of insulin until the optimum dose is determined. "We are looking to identify individual patient characteristics that influence how much additional insulin individuals with type 1 diabetes need to cover high-fat meals," he says. "As we learn more about how dietary fat affects insulin control, we will apply our findings to improve treatment recommendations and outcomes for patients with diabetes."

They are also planning an intervention study to assess whether reducing fat intake would optimize glucose control. In the coming months, Dr. Wolpert also anticipates developing new guidelines for clinicians and patients to enable them to determine whether high-fat foods are a factor in glucose control and make appropriate nutritional changes.

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The study was funded by the Scripps Foundation, Juvenile Diabetes Research Foundation, Harvard Clinical and Translational Science Center, and the National Center for Research Resources.

About Joslin Diabetes Center

Joslin Diabetes Center, located in Boston, Massachusetts, is the world's largest diabetes research and clinical care organization. Joslin is dedicated to ensuring that people with diabetes live long, healthy lives and offers real hope and progress toward diabetes prevention and a cure. Joslin is an independent, nonprofit institution affiliated with Harvard Medical School.

Our mission is to prevent, treat and cure diabetes. Our vision is a world free of diabetes and its complications. For more information, visit http://www.joslin.org.

About Joslin Research

Joslin Research comprises the most comprehensive and productive effort in diabetes research under one roof anywhere in the world. With 30‐plus faculty level investigators and an annual research budget of $36 million, Joslin researchers focus on unraveling the biological, biochemical and genetic processes that underlie the development of type 1 and type 2 diabetes and related complications.

Joslin research is highly innovative and imaginative, employing the newest tools in genetics, genomics and proteomics to identify abnormalities that may play a role in the development of diabetes and its complications. Joslin Clinic patients, and others with diabetes, have the option of participating in clinical trials at Joslin to help translate basic research into treatment innovations.

Joslin has one of the largest diabetes training programs in the world, educating 150 M.D. and Ph.D. researchers each year, many of whom go on to head diabetes initiatives at leading institutions all over the globe. For more information, visit http://www.joslinresearch.org.

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