By Amy E. Hamaker

Have you ever felt driven to eat something sweet, even when you didn’t want to? The reason for this drive may be the high levels of sugar, fat and salt in food, which produce a dopamine hit that alters brain chemistry, according to David Kessler, MD, professor of pediatrics and epidemiology and biostatistics at the University of California, San Francisco, School of Medicine.

Kessler’s comments came during his lecture on Nov. 12 as part of the Dean’s Distinguished Lecture Series, held in Mayer Auditorium. His focus was from his book, The End of Overeating: Taking Control of the Insatiable American Appetite.

Keck School Dean Carmen A. Puliafito, MD, MBA, introduced Kessler, reminiscing about their shared time together as classmates at Harvard Medical School. Kessler’s career includes time as the head of the U.S. Food and Drug Administration, and dean of the medical schools at Yale University and the University of California, San Francisco. Kessler became interested in obesity in 2008.

David Kessler, MD, interacts with Keck School of Medicine of USC students, staff and faculty about why people feel compelled to overeat.
(Photo/Jon Nalick)

During his presentation, Kessler noted that adult weight in the United States remained relatively stable during the 1960s. However, over the past four decades, adult weight has steadily increased. “People are entering their 20s 18 pounds heavier on average,” he said. “Weight set points are a myth; if there was a weight set point, we wouldn’t be getting bigger.”

In animal studies, said Kessler, animals would normally habituate to foods with fat, salt and sugar — meaning that they lose their cravings for these foods when they were presented on a limited basis. However, animals do not habituate to wanting the combination of fat, sugar and salt when regularly fed what he calls a “supermarket diet,” high in foods containing a combination of fat, sugar and salt.

Kessler added that there are cues to hunger (such as sight, smell and memories) that trigger reward associations — much like Pavlov’s dogs were trained to associate a ringing bell with food. This can cause feelings of loss of control over eating, lack of satiation and obsessive thoughts about food as responses to this conditioning.

“We’re wired to focus attention on the most salient stimuli, and food today is designed by food producers to achieve a remarkable salience,” Kessler explained. “Our behavior in overeating and eating a poor diet becomes rewarding and self-sustaining. We’re living in a food carnival; what did we expect to happen?”

To combat this “programming,” Kessler recommended changing people’s perception. “We could demonize tobacco, as it isn’t necessary for living, but doing the same to food is the stuff of eating disorders,” he said. “This isn’t about regulations, laws and litigation, but changing how we perceive things like large portion sizes and fast food.”