October 10, 2008

Study to chew the fat on popular diet

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Heidi Silver, Ph.D., shows off some of the supplies donated for the study of dietary fat consumption. (photo by Joe Howell)

Study to chew the fat on popular diet

Vanderbilt University Medical Center investigators are using a modified version of the popular low-carb Atkins diet to determine if the type of dietary fat consumed is even more important than the amount of fat eaten.

Heidi Silver, Ph.D., and Kevin Niswender, M.D., Ph.D., want to find out whether there are differences in weight loss, energy expenditure, and risk factors for diabetes and heart disease based on the type of fats being consumed.

“Although we support current public guidelines that tell us that the amount of fat we consume is unhealthy, and that we need to lower the amount of saturated fat in our diets, we also recognize that there is not enough information about how different types of fat and other nutrients affect weight loss and risk factors for related chronic diseases,” Silver said. “And the obesity problem is not going to be solved just by telling people to reduce the amount of fat that they eat.”

The study will examine which of the commonly consumed 18-carbon fatty acids has the best health effects in a dietary intervention with 164 women, age 21-50, who have a Body Mass Index (BMI) between 30-39.9.

Funded for two years by the Dr. Robert C. and Veronica Atkins Foundation, it uses a relatively high-fat, relatively low-carbohydrate meal plan, and dietary supplements.

“We designed the study targeting women because much prior research on diabetes and heart disease has targeted men, and because we have information from other studies that shows a different pattern of weight loss in women,” Silver said.

“Furthermore, we are targeting pre-menopausal women because levels of the hormone estrogen have a relationship with comorbidities of obesity and risk for chronic diseases.”

Study participants will eat healthy sources of both animal and plant-based fats during the 16-week study and take a dietary supplement derived from one of three different 18-carbon fatty acids or a placebo.

Silver said she was initially concerned with the timing of the study because food and gas prices are on the rise and food economics research has shown that foods that are considered being the healthiest are often the most expensive.

She received generous donations from various food boards (almond, peanut, sunflower seed, hazelnut, and pistachio) to alleviate cost concerns.

“Our participants receive a variety of fats and oils including margarine, salad dressing, vegetable oil, nuts, seeds and Atkins snack bars — as well as utensils like measuring cups to help with their weight management,” she said.

This study, unlike other dietary interventions, is modeled after clinical drug trials that use pills and include a placebo. Silver said she searched far and wide for fatty acid supplements that meet all of the safety criteria for human consumption.

“If you look at the literature where fat content of the diet has been studied, you will see that usually a food item such as a muffin or cookie is designed with the fat content altered,” Silver explained.

“But the muffin or cookie also has a lot of other ingredients that can affect body weight or disease risk factors. So what we are doing, using pure fatty acids instead of foods, has not been done before in a weight loss setting.”

Silver said the study is considered translational research because it builds on findings from fatty acid research conducted in Niswender's basic research lab and applies it to humans in a randomized, controlled fashion.

“Certainly, clinical practitioners realize that a one-size-fits-all approach to weight loss and chronic disease does not work, so we hope to expand our knowledge and options that can be used in healthy weight loss interventions for a variety of people.”

For more information on the study call 936-0985.