ASU PhD student recognized at American Physiology Summit for obesity research

As obesity rates continue to rise in the United States, researchers are racing to answer a deceptively simple question: Why do some bodies respond differently to exercise, diet and weight-loss treatments?

For Kailin Johnsson, a PhD student in Arizona State University's School of Life Sciences, that question is at the center of her research, which recently earned her national recognition.

At the 2026 American Physiology Summit, Johnsson received the Endocrinology and Metabolism Research Award and earned two additional distinctions for her research abstract: the Walter B. Cannon Lecture Abstract of Distinction, and the Endocrinology and Metabolism Research Section Abstract of Distinction. Out of more than 1,000 submitted abstracts, only a handful received the Walter B. Cannon distinction.

“It was really cool,” Johnsson said of receiving the honors. “We weren’t expecting to get any awards.”

Johnsson, who is finishing her third year in her biology PhD program focusing on muscle physiology, studies how obesity affects the body’s ability to build and maintain muscle after exercise.

She performs her research in the Human Obesity Metabolism (HOMe) Lab at ASU’s Health Futures Center, led by Christos Katsanos, associate professor in the School of Life Sciences, and in collaboration with Eleanna O. De Filippis at Mayo Clinic. Her work presented at the American Physiological Society examined how aerobic exercise influences muscle protein synthesis in individuals with obesity. This research could eventually help scientists develop more personalized exercise and nutrition strategies.

Normally, exercise combined with amino acids, which are essentially the building blocks of protein, stimulates muscle protein synthesis — the process that helps muscles grow and recover. Researchers expected to see that response in participants with obesity, even if it was somewhat reduced. Instead, Johnsson and her collaborators found that the response was significantly blunted immediately following aerobic exercise.

Describing the team’s surprise at the findings, Johnsson said: “We had all the parts and we put them all together, but the machine didn’t turn on as expected.”

The results provide new insight into the complex interactions between exercise, nutrition and metabolic health. They also contribute to a growing body of research suggesting obesity may involve underlying cellular or metabolic dysfunctions that cannot be explained by diet and exercise alone. That broader question — why some bodies respond differently under the same conditions — is what drives much of Johnsson’s research.

While weight loss is often framed as a matter of calorie deficits and exercise routines, Johnsson said emerging evidence suggests the biology of obesity may be far more complicated.

“Eating in a calorie deficit, you will absolutely lose weight,” she said. “But the biology behind obesity is more complex. Two people can be in a similar caloric deficit and still lose weight differently, which raises the question, what physiological mechanisms are driving those differences?”

Researchers are increasingly investigating whether muscle in people with obesity becomes “exercise resistant” — meaning it responds differently to nutrients and exercise compared with muscle in lean people. Johnsson said her findings add to growing evidence that something is altered at the cellular level in the muscles of humans with obesity.

“Obesity makes it harder for the muscles to make new protein after exercise, even when the body has enough nutrients,” she said.

The work arrives at a moment when GLP-1 medications such as Ozempic and Wegovy are rapidly reshaping conversations around obesity and weight loss. Their laboratory is now beginning to investigate another unanswered question: Why do some patients taking those medications lose large amounts of muscle mass while others do not?

“We have no idea why,” Johnsson said. “Some people seem to preserve muscle very well, while others lose much more than we would expect, and we still don’t fully understand what’s driving those differences.”

Ultimately, the goal is to better understand how obesity changes the body’s metabolism so researchers can develop more effective support strategies. Johnsson said the findings could eventually help scientists identify better timing for exercise and nutrition interventions or develop more targeted recommendations for people with obesity.

“What we’re seeing is that, in obesity, even when you provide the normal stimuli that should support muscle building — like exercise and amino acids — the immediate response does not appear to be the same as it is in leaner individuals,” she said.

The research itself requires extensive clinical collaboration between ASU and Mayo Clinic. Participants undergo exercise testing, blood analysis and muscle biopsies, allowing researchers to measure how muscle builds protein before and after exercise. Tissue samples are collected from the vastus lateralis — a muscle in the upper thigh known for high protein turnover activity — then processed across multiple research sites, including the Health Futures Center and Mayo Clinic laboratories.

For Johnsson, one of the most rewarding parts of the work is its immediate connection to human health and patient care.

Attending the American Physiology Summit also gave Johnsson an opportunity to connect with researchers from around the world studying many of the same questions. She said the conference reflected how quickly the field is advancing as obesity research gains momentum and technologies become increasingly precise.

“There were so many scientists sharing their breakthroughs and new approaches that had been working,’” she said. “I think everyone left feeling like we all have new ideas to test and new directions to explore.’”

The laboratory is already preparing for its next phase of presentations, including an upcoming international conference in Switzerland where Johnsson will discuss GLP-1 medications and muscle loss variability. Future studies will follow patients over time to better understand how these drugs affect muscle protein synthesis and muscle loss.

As researchers continue searching for answers, Johnsson believes the field is getting closer to understanding the biological mechanisms driving obesity and metabolic dysfunction — knowledge that could eventually improve care for millions of people.

“If we can find the reason,” she said, “we could find a solution.”