A recent study highlights the role of dopamine as the pleasure and reward center of the brain. The evolution of the human experience has led us away from eating as much food as possible as a survival strategy when food was scarce to eating on demand, often excessively, without expending an energy counterbalance. The authors of the study, published in Current Biology, point out that food overindulgence not only affects our sleep-wake cycle clock, but also inhibits obtaining adequate rest and appropriate caloric intake, leading to obesity and diseases, such as diabetes.

Ali Güler, senior author and professor of biology at the University of Virginia, said, “Many of these foods are high in sugars, carbohydrates and calories, which makes for an unhealthy diet when consumed regularly over many years,” adding, “prior to the advent of our electricity-powered society, people started the day at dawn, worked all day, often doing manual labor, and then went to sleep with the setting of the sun. Human activity, therefore, was synchronized to day and night. Today, we are working, playing, staying connected, and eating—day and night.” This, Dr. Güler said, affects our body clocks, which were evolved to operate on a sleep-wake cycle timed to daytime activity, moderate eating, and nighttime rest. “This lights-on-all-the-time, eat-at-any-time lifestyle recasts eating patterns and affects how the body utilizes energy,” Dr. Güler noted. “It alters metabolism—as our study shows—and leads to obesity, which causes disease.” 

The researchers employed mice models to demonstrate that high-fat foods, those associated with pleasure when consumed, are linked to both dopamine production and release, as well as disrupted biological schedules that can lead to overeating, obesity, and, ultimately, health issues. By feeding mice “rewarding food” heavy in sugar and allowing them to snack 24/7, and comparing that cohort to mice fed normal (wild) diets, the researchers found that the mice eating high fat and calories ate larger portions and ate more frequently, resulting in obesity. Conversely, mice that maintained the normal (wild) schedule and diet type did not pursue round-the-clock eating. The authors stated that this demonstrates the unique role of dopamine signaling in disrupting the central circadian clock and promoting overconsumption outside of mealtimes. 

In their conclusion, the authors highlighted that their findings define a connection between the reward and circadian pathways in the regulation of pathologic calorie consumption. According to Dr. Güler, “We evolved under pressures we no longer have.” He added, “It is natural for our bodies as organisms to want to consume as much as possible, to store fat, because the body doesn’t know when the next meal is coming.

“But, of course, food is now abundant, and our next meal is as close as the kitchen, or the nearest fast-food drive-through, or right here on our desk. Often, these foods are high in fats, sugars, and therefore calories, and that’s why they taste good. It’s easy to overconsume, and, over time, this takes a toll on our health,” said Dr. Güler.

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