CHAPEL HILL, NC - The Center for Health Promotion and Disease Prevention (HPDP) at the University of North Carolina at Chapel Hill has received a five-year, $3.8 million grant from the National Heart, Lung, and Blood Institute (NHLBI) to fund research that will address the challenge of achieving long-term weight loss among patients with obesity cared for at primary care practices. Co-led by Thomas Keyserling, MD, MPH, from the department of medicine, and Carmen Samuel-Hodge, PhD, RD, from the department of nutrition, the randomized, controlled trial will test the effectiveness of a behavioral weight loss program promoting an adapted form of the Mediterranean diet.
"This study is unique in its approach since most weight loss interventions have not promoted what we now know to be a healthful dietary pattern, which aligns very well with a Mediterranean diet," said Keyserling. "It includes generous intake of high-quality fats, mostly from nuts and vegetable oils, and high-quality carbohydrates, which include fruits, vegetables, and whole grains. A healthful dietary pattern is associated with substantial reductions in cardiovascular disease risk and diabetes risk, even without weight loss."
Patients with obesity are more likely to have diabetes and both conditions put them at increased risk for cardiovascular disease. Most previously studied weight loss interventions have focused only on weight loss as a goal, instead of also targeting cardiovascular disease. Rather than focusing on diet quality, most interventions have emphasized calorie reduction and have not yielded significant reductions in cardiovascular disease events or mortality.
Mediterranean-style diets have been shown to reduce cardiovascular disease events like heart attack and stroke, but only a few studies have tested whether this type of eating regimen effectively promotes weight loss. Research is particularly limited in the United States, where trials have only been conducted with urban residents who were primarily white.
Researchers at HPDP have developed a Mediterranean-style diet, termed "Med-South," that is adapted to the cultural and taste preferences of residents living in the southeastern U.S. It incorporates foods like peanuts and peanut butter, which have health benefits similar to tree nuts. Researchers also created a cookbook that features adapted recipes for healthier versions of popular foods in the southeast like barbecue and hushpuppies.
In previous studies, this dietary pattern was well-received by patients and improved diet quality, weight loss, and blood pressure, but it has yet to be tested for weight loss in a randomized, controlled trial.
"This grant will give us the opportunity to carefully assess the impact of the Med-South weight-loss program when evaluated in a rigorous randomized trial," said Keyserling. "Our hope is that the intervention will help participants make dietary changes that can be maintained over time and yield long-term weight loss along with improvement in cardiovascular risk factors."
The new study will enroll 350 participants at five primary care practices in central North Carolina. The study team will randomize patients such that half will participate in the Med-South program and half will receive referrals to either the weight-loss program at their clinic or a community-based program. During the first phase of the Med-South program, patients will participate in a four-month lifestyle intervention focused on the "basics" of healthful eating, with an emphasis on fat and carbohydrate quality, rather than weight loss.
"The first phase of this intervention will prepare participants for the weight loss phase by teaching them a set of 'stability skills,' which include learning to eat a healthful diet without feeling deprived, becoming comfortable with frequent self-weighing, and navigating inevitable disruptions," said Carmen Samuel-Hodge. "In previous studies, this type of approach has been associated with better weight-loss maintenance."
After this introduction, participants will enter an eight-month phase focused on weight loss, followed by a year-long period of weight loss maintenance. While the primary outcome measured by the trial will be weight loss, researchers will collect other data which may show additional benefits of the Med-South diet. The study team will measure blood markers of inflammation, which are known to improve with better diet quality. Using a Veggie Meter™, a device that employs emerging non-invasive reflection spectroscopy technology, researchers will also measure participants' skin carotenoid levels, which increase with greater fruit and vegetable consumption.
"We are pleased that our Center has the opportunity to conduct this study, which builds on our prior research evaluating healthful dietary interventions for residents of North Carolina," said Alice Ammerman, DrPH, Mildred Kaufman Distinguished Professor of Nutrition and director of the UNC Center for Health Promotion and Disease Prevention.