Less than five minutes into his lecture, psychology professor Kelly Brownell posed this question: “Can you identify this food?” The slide displayed a list of 56 ingredients, and the students crowded into Davies Auditorium laughed before calling out answers ranging from cookies to breakfast cereals. One contestant responded correctly: a Kellogg’s pop tart.

“That’s right,” Brownell said. “But the scary thing is it could really be any one of those foods.”

Brownell, director of Yale’s Rudd Center for Food Policy and Obesity, left an impression with this initial slideshow on nutrition for his undergraduate class, “The Psychology, Biology and Politics of Food.” The more than 300 students shopping the lecture chatted excitedly when they left the room an hour later, after seeing images of baby bottles branded with popular soft drink names and learning that 100 percent of U.S. children are able to identify Ronald McDonald.

Students who took Brownell’s lecture when it was first offered two years ago said they found the class appealing because of its relevance to today’s world, particularly on college campuses, where students are faced with changes in eating habits as they adjust to campus life.

“It incorporated so many different aspects of society,” Kendra Emhiser ’07 said. “I didn’t realize how they affected my own life, and it made me think about what I ate on a daily basis.”

But Brownell said he is not content merely to change students’ conceptions about advertising, what they eat, and how their bodies process that food. He hopes that if they decide to take his class, they will become activists who aim to make the world better in a time when nutrition issues have drawn increasing attention from the national media.

An internationally renowned expert on nutrition, obesity and public policy, Brownell has advised members of Congress, world nutrition organizations and media leaders on these issues. He was named one of the 100 most influential people in the world by Time magazine last year and is recognized as a crusader against the food industry who takes a tough stance on marketing directed at children.

Despite his national recognition — he even earned a spot in the Academy Award-nominated documentary “Super Size Me” — Brownell said he still values mobilization on a grass-roots level. Each student enrolled in his class has the option of conducting a final project that involves the Yale or New Haven community in activism concerning nutrition, and is required to submit an op-ed article on food-related issues to a professional publication.

Lawrie Peck ’09, who is currently enrolled in Brownell’s class, said she thinks the professor does a good job of making these nationwide health issues accessible and relevant to a college audience.

“I think many of the students in our class don’t realize how well-known he is in this field, but he’s amazingly good at relating to kids our age.”

Brownell tries to use his undergraduate class as one way to get out the message to those he believes can effect change, although he said he knows not everyone may agree with his sometimes-controversial opinions.

“I go into this knowing that this may help change them in a direction I don’t like, but most Yale students want a better world, and I hope to engage them in ways so they become active,” he said. “I believe teaching students how to be agents of change in academics is unusual but needed.”

Stacy Ruwe, executive director of the Rudd Center, said Brownell’s work is crucial to the health crisis in modern American society.

“His research and advocacy confirms that our toxic environment, where we are bombarded with enticements to eat unhealthy foods as we have less time and fewer opportunities for physical activity, is the result of large-scale social changes, not merely personal failures of willpower,” Ruwe said.

Brownell did not take much interest in nutrition or media at a young age. He said he found his passion by accident while in graduate school at Rutgers University nearly 30 years ago. After receiving his bachelor’s degree from Purdue University in his native Indiana, he was pursuing a doctorate in clinical psychology and was assigned to conduct research on what he calls the “amazing intersection” between biology, psychology, the environment and public policy.

After additional training at Brown University, Brownell then joined the faculty of the University of Pennsylvania School of Medicine, where he performed clinical trials aimed at treating obesity and studied social influences on the epidemic. He came to Yale in 1990, where he has served as the master of Silliman College for six years, as well as chair of the Psychology Department.

Brownell was the first to propose a tax on unhealthy food with the revenue earmarked for nutrition, and he has devised other innovative food-policy reforms, including the removal of soda machines from public schools and a ban on advertising directed at children similar to those in European countries.

He blames a toxic American culture for the obesity crisis, and points to marketing directed at children, the fundamental economy of food today, portion size and sedentary behavior as the primary obstacles. He said he believes people are being deluded into thinking the government is doing more than it is, which stalls things even further.

Instead of politicians protecting the food industry, Brownell said, he wants them to be honest and support public health.

“Who should be the referee? How do you decide what’s the truth? To me, science should be the referee, and the science says it’s hurting kids,” he said.

As director of the Rudd Center, which opened last October, Brownell works in research and advocacy with the goal of improving the world’s diet through science, dialogue and policy.

In a field that is constantly changing, he said the center’s goal is to take an interdisciplinary and objective approach to combat the obesity epidemic.

“We want to make a difference,” Brownell said. “We don’t just want to study things. We want to accelerate change by working with, through and, when we need to, against big institutions such as government and the media.”

Arkansas Gov. Mike Huckabee, an outspoken advocate for better nutrition, applauded Brownell as a crusader against the fast-food industry in his Time magazine profile. But he also wrote that the professor oversimplified the problem, arguing that placing a tax on calories would only penalize the poor.

Brownell continues to believe that a tax on unhealthy food is a way to enact change, he said, and equates billboard images of Ronald McDonald with those of the Marlboro man. As his field continues to gain increasing national attention, he said, he is excited to see what comes next in terms of governmental policy and corporate reaction.

“It feels to me like we’re on the verge of things tipping in a much better direction,” Brownell said. “Now the challenge is, what do you do? History is being written right now.”