What Makes Us Overeat?
To some extent we’ve been programmed to overeat since the days our ancestors hunted and gathered on the African savanna.
Having the capacity to binge on huge quantities of food whenever it became available was probably an evolutionary advantage in an environment where food supplies were erratic and scarce. So anytime we see or smell food, several systems kick in simultaneously in various parts of the brain to make sure we don’t miss the opportunity to chow down.
The brain’s reward and motivation system gets fired up (“I must have that pizza now!”), while centers of the brain that link to emotion and memory switch into higher gear (“The last time I had pizza, it made me happy!”). At the same time, the brain’s pleasure centers are activated (“Pizza is yummy!”), with the most high-calorie foods causing the most stimulation (“Pizza with double cheese and pepperoni is even yummier!”). The result? Too often we dig in, hungry or not.
These overlapping systems made sense on the savanna, ensuring we’d always seek out the calorie-packed foods that offered the most insurance against famine. But for most of us living in America today, every day is a feast, not a famine. Ads for doughnuts and soda confront us every time we pump gas, and cinnamon buns and pretzel aromas fill every shopping mall. That means our brains’ appetite systems are in a frequent—sometimes constant—state of arousal, experts say. “If you’re the type who lights up at the sight or smell of food, just shopping at the mall is a barrage,” says Bulik. “You can’t even go to a bookstore anymore without being bombarded by the smell of baked goods and coffee. You have to be vigilant almost all the time.”
What makes us decide to eat, or not eat, begins in the hypothalamus, a key control center at the base of the brain, explains Mary Boggiano, Ph.D., a psychologist at the University of Alabama at Birmingham who has extensively researched neurochemical changes associated with dieting and binging. “The hypothalamus is what induces satiety or hunger, depending on our caloric needs,” she says. “But when it comes to binge eating, which really isn’t about true hunger or satiety, normal hypothalamic function may get overpowered.” The parts of the brain that govern rational responses, like the neocortex (“I need sleep, not that pint of Ben & Jerry’s”) get overridden, too, she explains. What seem to win out are other, connected brain structures that form the “feeling parts of the brain,” she says—regions like the amygdala (which plays a role in attaching emotional meanings to various stimuli) and the nucleus accumbens (involved in emotions, addictions and pleasure-seeking behavior). For some of us, this inner war with our rational sides and our primal urges to stock up on calories happens dozens of times daily—or more. Consider that we’re confronted with an average of 200 food-related decisions to make every day, according to Brian Wansink, Ph.D., of Cornell University’s Food and Brand Laboratory and an EatingWell advisory board member.
The overstressed lives most of us lead today make the picture even more complicated. “We’re also hard-wired to store up calories to deal with stress,” says Boggiano, recalling that primordial savanna. “In those days, stress involved events where we needed energy. It was important for the body to have plenty of calories if it was being attacked by a saber-toothed tiger.” Food fuels muscles to launch a life-saving response (something along the lines of “Run for your life!”)—so “it makes sense for survival that stress and food are coupled,” she adds.
But in modern life, most of the stresses we face are the sedentary, nonfuel-requiring type—like that overdue presentation that must be finished tonight or the simmering feud with a nasty in-law. Nonetheless, the vestigial connections between food and stress remain—and we turn to food to soothe, or distract us from, our stressful emotions, especially if we have a tendency to binge. There’s a reason why we often turn to chocolate, cake and other treats. Anything high in sugar and fat causes opioids—“feel-good” chemicals like endorphins—to be released in the brain, which replace stressed-out feelings with pleasurable ones. Researchers from Boggiano’s lab and from the University of California, San Francisco, also found that sugary, fatty foods seem to help suppress levels of a key stress hormone, adrenocorticotropic hormone (ACTH).
“Of course, for bingers and other disordered eaters, overeating in response to stress becomes a stressor in itself,” notes Boggiano. “It becomes a vicious cycle of feeling bad about overeating, then eating more to distract from the guilt.”
Read more: Change the way you think about food