In the four years from 1976 through 1980, 15 percent of American adults were obese. In 2020, another 35 percent joined the fray—about 40 percent of adults are now obese. Obesity’s rise is correlated with increases in heart disease, diabetes and other complications (eg joint degradation and hypertension) related to obesity.
The demand for more convenience has spurred the food industry to cheaply mass produce foods that not only add the pounds but the points in blood pressure, blood sugar and cholesterol. “The diet in the U.S. and other nations has changed dramatically in the last 50 years or so, with highly processed foods readily and cheaply available at any time of the day or night,” commented Ali Güler, a professor of biology at the University of Virginia. “Many of these foods are high in sugars, carbohydrates and calories, which makes for an unhealthy diet when consumed regularly over many years.”
In a study published in the journal Current Biology, Güler and his colleagues have shown that the pleasure center of the brain that produces dopamine in concert with the brain’s biological clock that regulates daily physiological rhythms collaborate, and that high-calorie foods that evoke pleasure disrupt normal feeding schedules, resulting in overconsumption, itself leading to weight gain and obesity.
Güler’s team found that mice fed a diet comparable to a wild diet in calories and fats maintained normal eating and exercise schedules and therefore, proper weight. But mice fed high-calorie diets laden with fats and sugars began “snacking” at all hours and became obese.
Additionally, mice that had their dopamine signaling disrupted—meaning they didn’t seek the rewarding pleasure of the high-fat diet—maintained a normal eating schedule and did not become obese, even when presented with the 24/7 availability of high-calorie feeds.
“We’ve shown that dopamine signaling in the brain governs circadian biology and leads to consumption of energy-dense foods between meals and during odd hours,” Güler said.
Other studies have shown that when mice feed on high-fat foods between meals or during what should be normal resting hours, the excess calories are stored as fat much more readily than the same number of calories consumed only during normal feeding periods. This eventually results in obesity and obesity-related diseases, such as diabetes.
The modern human diet of convenience and abundance is calorie-dense; for example, Güler explained, “The calories of a full meal may now be packed into a small volume, such as a brownie or a super-size soda. It is very easy for people to over-consume calories and gain excessive weight, often resulting in obesity and a lifetime of related health problems.”
Grippo et al. “Dopamine Signaling in the Suprachiasmatic Nucleus Enables Weight Gain Associated with Hedonic Feeding.” Current Biology, 2020; DOI: 10.1016/j.cub.2019.11.029