Fighting Obesity at the Cellular Level

Anyone who has ever cooked with onions knows about the peel. It’s the dry, translucent outer layer that crinkles like paper as it’s ripped from the edible bulb.

But onion peel contains a concentrated substance that has antioxidant and anti-inflammatory properties. Hye Won Kang, Ph.D., a molecular nutritionist at North Carolina A&T State University, is exploring how this substance works in the intestine — and how it might be a new tactic in the ongoing fight against obesity.

“My new research is looking at the intestine, which acts as a barrier,” Kang said. “The intestine is where people develop chronic metabolic diseases. That’s why it’s important to understand how the intestine regulates the kind of food people can absorb and help protect individuals from harmful environmental factors.”

Kang is a professor of family and consumer sciences in A&T’s College of Agriculture and Environmental Sciences. While she was promoted to that rank in 2025, her research into nutrition, health and obesity goes back more than two decades.

Kang began studying nutrition as an undergraduate in her native South Korea. For her master’s degree, she investigated functional foods — foods that provide health benefits beyond their nutritional value — and dietary compounds. As a doctoral student at the University of Connecticut, she delved into molecular nutrition and biochemistry to learn more about human metabolism. After earning her doctorate degree, Kang conducted medical research at Boston’s Brigham & Women’s Hospital, which is affiliated with Harvard Medical School. Her primary research areas during those six years were diabetes and obesity.

Obesity remains a significant concern in the United States. According to the Centers for Disease Control, rates of both obesity and severe obesity have been on the rise for decades. Currently, 40% of American adults are considered obese, which puts them at greater risk for chronic health conditions such as hypertension, type 2 diabetes and coronary heart disease.

“Most people become obese because of processed food and high-fat diets, and it’s very difficult for them to cut down on food portions,” Kang said. “What I hope to do with my research is help them improve their health by making the food they’re consuming on a daily basis healthier.”

Since joining the CAES faculty in 2013, Kang has investigated the obesity-reducing impact of bioactive compounds derived from food byproducts. The focus of her research is a plant pigment known as quercetin. Quercetin is a flavonoid — a chemical compound with anti-oxidant and anti-inflammatory properties — that’s commonly found in foods such as red wine, green tea, berries and apples. It’s the major bioactive compound of onion peel and gives onion peel its orange color. Using onion peel waste sent by a food manufacturing company in Oregon, Kang makes her own onion peel extract in her Carver Hall lab.

Early in her A&T tenure, Kang focused on using quercetin to reduce fat in the body. Humans and other mammals have two types of fat cells: white fat, which stores extra calories as energy (and leads to obesity when too much fat accumulates inside them); and brown fat, which releases energy as heat to keep the body warm.

Activating brown fat holds promise for reducing white fat by releasing heat that burns fat. Her research found that quercetin extracted from onion peel reduced inflammation in brown fat and help brown fat work more efficiently in obese mice. Her research also revealed that quercetin activated a brown-fat effect in white fat in mice that caused white fat cells to release some of their stored energy rather than retain it. Interestingly, Kang also saw that quercetin improved gut microbiome in obese mice.

Kang examines onion skins in her Carver Hall lab. Quercetin, the major bioactive compound in onion peel, has both antioxidant and anti-inflammatory properties.

That latter finding caused Kang to extend her research to investigate the anti-inflammatory effect of quercetin on intestinal cells and their molecular mechanisms. With her new study, she’s looking for new ways to improve intestinal function and prevent systematic intestinal inflammation and oxidative stress that can lead to obesity and other diseases. Her current research is supported by a U.S. Department of Agriculture Evans-Allen grant of $1,478,474.

Other CAES colleagues see the potential of Kang’s work with quercetin. As the campus expert on onion peel extract, Kang has consulted with the faculty in the Department of Animal Sciences, who have added onion peel to livestock feed to study quercetin’s effects on carbon dioxide and methane emissions and on Salmonella infection.

Kang’s intestinal cell research has some potentially far-reaching implications for humans as well. Onion peel extract could be developed into a supplement that could enhance the health effects of foods eaten every day. Using onion peel as the source of a supplement could reduce some of the billions of tons of food wasted every year in the United States. And it could give nutritionists another healthy tool to counteract the national epidemic of obesity.

In the meantime, Kang continues to dig deeper to learn even more about how quercetin regulates the activities of intestinal cells. Gaining more understanding of this molecular mechanism might lead to further discoveries to treat diabetes and other chronic diseases.

“We still have so many questions,” Kang said.