When kinesiology assistant professor Todd Hagobian was an undergraduate student at University of Southern California, he was training on his bike seven days a week. He’d bike anywhere from one to five hours a day, while only taking a day off once every two or three weeks. And after every workout, he always noticed the same thing — he wasn’t hungry.
“I noticed when I did these big, long events in cycling, I didn’t eat that much for the rest of that day,” Hagobian said. “The subsequent days I would start to eat a little bit more, but that day I just wasn’t hungry.”
Years later, Hagobian, working with a team of students and faculty, set out to research the effect exercise had on hunger. And after a year-and-a-half study, the group’s work was published in The Journal of Applied Physiology last month and found itself the subject of a New York Times article.
“It’s not until the last four or five years that there has been any data on this, it is a relatively new field in terms of the regulation of appetite or food intake and how exercise can affect that,” Hagobian said. “People thought it doesn’t affect it really, before that.”
But Hagobian’s findings suggest it does. He, along with co-authors Nero Evero, who was a graduate student in kinesiology during the time of study; Laura Hackett who graduated from Cal Poly in June with a bachelor’s degree in kinesiology; and fellow faculty members Suzanne Phelan and Robert Clark found brain activity in regions that stimulate hunger were significantly reduced following exercise.
“The data is actually pretty clear that when people exercise, they don’t eat as much as if they didn’t exercise,” Hagobian said. “Exercise affects the brain centers that regulate food intake. Those centers are suppressed, so there is no stimulus to eat or there is less stimulus to eat.”
The group arrived at that conclusion after starting data collection in fall 2010 when they began sending subjects to Templeton Imaging Medical Corporation. There, the subjects were hooked up to Functional Magnetic Resonance Imaging (fMRI), which measures brain activity by gauging blood flow, and asked to either exercise rigorously on a training bike or sit for an hour.
Afterwards, the subjects were shown images of high-calorie, typically fatty, foods and healthy, low-calorie foods. The fMRI would then scan areas of the brain, revealing the brain’s interest.
The results came back definitively and were consistent with the fact that exercise suppresses hunger.
“I was surprised at the robustness, meaning that we had a lot of regions that showed decreased activity,” Hagobian said. “I expected only one or two regions to change, and I think that we had eight or 10 different regions that changed.”
Because of the definitive results, the authors have started incorporating their practices into their daily lives, especially Hackett. She is now in an accelerated bachelor’s degree program for nursing at Mount St. Mary’s College in Los Angeles, and her background with the study is helping her emphasize the importance of exercise to patients she deals with on a daily basis.
“When you get down to the nuts and bolts of it, it all applies,” Hackett said. “That little bit of exercise a day makes a huge difference. If you can get people who I see in the hospital every day to make small changes in their lives, it would totally change who is actually in the hospital from day to day. It’s neat to be able to apply it and apply my background and really see how it correlates to what I am doing now.”
Even others outside the study have felt those changes in appetite, such as kinesiology sophomore and STRIDE Club president Laura Cox. She said she typically runs three-and-a-half miles every other day of the week and weight trains for two-and-a-half hours during the days between.
And after those workouts, she usually isn’t hungry.
“I find it more after I run,” Cox said. “When I get back, food doesn’t usually sound too good. It is hard to say with weight training. I don’t feel that hungry, but I still make myself drink a protein shake, or chocolate milk, or something like that.”
This effect may create more reason for people to get active, Evero said. In exposing the connection between appetite and exercise, the results of the study could lay down the groundwork for creating a more healthy society.
“No study proves anything,” Evero said. “But I am a strong believer in the power of exercise, and I truly believe what we studied is essentially a link to proper exercise intervention.”
Others such as kinesiology senior Megan Yamashiro agree. Yamashiro said she believes if the results alone won’t get people off their couches, but the results in combination with other advantages may.
“Even if people don’t exercise for appetite suppression, I hope they will do it for their health,” Yamashiro said. “There are so many mental, physical benefits of exercise, this is just another thing to add on to all the benefits established.”
It’s also something Hagobian’s started incorporating in his lectures. He said he plans on doing a follow-up study on a more diverse group of subjects, but the original has already spurred a lot of praise and feedback, especially after it appeared in The New York Times.
All in all, Hagobian said he was excited the study got the press that it did, because of how hard every student involved worked on the study.
“We publish stuff in these journals and there is more readership in that one New York Times article than in any of the other journals. It’s not even close,” Hagobian said. “I am happy for all the students that were involved in it.”