Looking for Answers Before Birth: How 2 UT Health Sciences Researchers Are Re-examining Childhood Obesity

Dr. Hyo Young Choi (left) and Dr. Qi Zhao (right), both faculty members in the UT Health Sciences Department of Preventive Medicine, recently published a study exploring how the placenta, the temporary organ that connects a mother and her developing baby during pregnancy, may play a key role in shaping a child’s growth and future obesity risk.

Childhood obesity is often framed as a problem of habits, including what children eat, how much they move, and the environments in which they grow up. But researchers at the University of Tennessee Health Sciences began asking a different question: what if some of the risk for obesity is set in motion long before a child takes their first steps, or even their first breath?

That question would ultimately bring together two scientists, a rare long-term study, and an unexpected biological clue hidden in an organ most people rarely think about: the placenta.

When Hyo Young Choi, PhD, joined the UT Health Sciences Department of Preventive Medicine in 2021, she was introduced to the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) study by its director, Qi Zhao, PhD. A longtime UT Health Sciences researcher and professor of epidemiology, Dr. Zhao has led CANDLE for years, overseeing one of the most comprehensive studies of its kind, following mothers and their children from pregnancy through early childhood while collecting detailed biological, environmental, and health data.

“The data were incredibly rich, especially for studying early development,” Dr. Choi said. “When Dr. Zhao told me about CANDLE, I knew it was a rare opportunity. I asked if we could talk more, and that conversation is what started this project.”

A Closer Look at the Placenta

Together, Dr. Choi and Dr. Zhao turned their attention to the placenta, an organ the researchers say is often overlooked.

“The placenta isn’t just a pipeline for nutrients,” Dr. Choi said. “It’s incredibly active. It controls which genes are turned on or off, helping guide how a baby grows and develops before birth.”

Using placental tissue collected at delivery from families enrolled in CANDLE, the research team examined gene activity and then followed the children’s growth, tracking height, weight, and body mass index (BMI) from birth through about age four.

Rather than relying on a single measurement, the researchers looked at growth trajectories, or patterns of growth over time. These patterns, Dr. Zhao explained, can be more revealing than a snapshot at one age. “For this study, we focused on early childhood, from birth to about four years old,” Dr. Zhao said. “That’s a critical window for growth and development.”

A Surprising Biological Signal

As the researchers analyzed the data, a striking pattern emerged.

“Certain placental genes were more active in children who showed faster growth or a higher risk of obesity early in life,” Dr. Choi said. “Many of these genes were involved in the immune system.”

That finding challenged some long-held assumptions.

“Traditionally, people think obesity affects the immune system,” Dr. Zhao explained. “For example, obesity in adults can weaken immune function. But what we’re seeing here is something different: the immune system may actually contribute to the development of obesity, starting very early in life.”

In other words, the biological groundwork for obesity may be laid before a child is even born, with immune-related genes in the placenta influencing how fat tissue develops later.

“This study highlights an important shift in how we think about childhood obesity, not simply as a condition shaped after birth based on day-to-day habits, but as one influenced by biology during pregnancy itself,” said Jessica Snowden, MD, vice chancellor for Research at UT Health Sciences. “By leveraging long-term cohort data and modern genomic approaches, Drs. Zhao and Choi are helping us understand how early-life biology can inform prevention strategies that begin before disease ever develops.”

Why This Matters for the Future

For Dr. Zhao, the study opens two important doors. The first is understanding mechanisms, or the biological “how.”

“We identified genes that may influence fat tissue development,” she said. “These are potential targets for future lab studies. Other scientists can now follow up on these genes to understand their specific functions.”

The second door leads to prevention. “Placental gene expression reflects what’s happening during pregnancy,” Dr. Zhao said. “That includes the mother’s metabolism, diet, health conditions like gestational diabetes, and even environmental exposures such as pollution or toxic chemicals.”

Because the CANDLE study collected extensive information from mothers during pregnancy, the team can now begin connecting those prenatal factors to changes in placental gene activity and, ultimately, to childhood obesity risk.

“We’re already doing follow-up work,” Dr. Zhao said. “We’ve analyzed metabolomics data from mothers during pregnancy and identified specific metabolites that influence the genes we found in this study. That’s a direct extension of these findings.”

“This work reflects what academic medicine is meant to do,” said Michael B. Hocker, MD, executive dean of the College of Medicine. “By asking important questions early and using long-term data thoughtfully, Drs. Choi and Zhao are helping us better understand how health and disease take shape long before symptoms appear. This kind of research moves us toward prevention and gives families a better chance at healthier outcomes from the very start, which is central to our vision of healthy Tennesseans and thriving communities.”

Starting Earlier to Make a Difference

Both researchers emphasize that childhood obesity remains a pressing public health challenge, and that waiting until problems appear may be too late. “Our contribution is identifying very early risk factors,” Dr. Zhao said. “If we can predict risk earlier and understand what influences it, we may be able to prevent obesity before it develops.”

For Dr. Choi, who has now been at UT Health Sciences for nearly five years, the project reflects the power of collaboration and long-term data. “This kind of research wouldn’t be possible without a study like CANDLE,” she said. “It allows us to see how pregnancy, biology, and early childhood are all connected.”

And for families, the message is hopeful.

“If we understand these early pathways,” Dr. Zhao added, “we may one day identify changes during pregnancy that support healthier growth for children from the very beginning.”