Snacking and Obesity

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It’s no secret that the US has a weight problem. Current statistics show that 33% of US adults are overweight and a whopping 40% are obese. In addition to this bump in weight gain are increased rates of cancer, diabetes, and heart disease. Other dire health consequences related to excess weight gain and lack of physical activity include high blood pressure and possibly Alzheimer’s disease. 1

According to Ali Guler, a biology professor at the University of Virginia, the prevalence of highly-processed, easily-accessible foods high in sugar and calories creates a very unhealthy diet over time. Guler and colleagues recently published a study in the journal Current Biology that found that the part of the brain that makes the chemical dopamine and the brain’s physiologic clock (that controls regular biological rhythms) are connected. High-calorie foods, which often provide pleasure, alter normal eating schedules, leading to overeating. 

Guler and his colleagues utilized mice for the study and imitated the 24/7 access of a high-fat diet, which found that snacking at random times resulted in obesity and related health conditions. Mice given calories and fat comparable to a wild diet sustained normal eating and exercise schedules and weight, whereas mice provided high-calorie, high-sugar, high-fat diets started snacking at will and became obese. 2

In addition, mice known as “knockout” mice -- where the signal for dopamine was disrupted and they did not look for the pleasure of a high-fat diet -- maintained a regular eating schedule and did not become obese, despite being given 24/7 access to high-calorie feedings. "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. 2

Guler notes that other research have shown that when mice are fed high-fat foods between meals or during a normal fasting period, these calories are more readily stored as fat compared to the same amounts of calories eaten during normal feeding times. These extra calories can lead to obesity as well as diabetes. 2

Americans often consume high calories in small volumes through high-fat desserts or big sodas, which leads to obesity and health consequences.

Guler believes our bodies are prone to eat as much food as possible when it’s available. This is related to a long previous history of hunting and gathering when humans had periods of plenty -- like after a kill -- combined with long periods without food. Because man was also possible prey to bigger animals, we seek food during the day and look for shelter and rest at night. 2

"We evolved under pressures we no longer have," Güler said. "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. Food is now abundant and our next meal is readily available and often high in fat, sugar and calories. Food that tastes good is easy to overeat, which impacts our health in the long run." 2

Our sleep-wake cycles have also been altered by the invention of electricity. Guler notes that we are working, playing, and eating both day and night whereas in the past, people began their days at dawn, did hard labor throughout the day, and went to sleep when the sun set. 2

Guler emphasizes that it’s not just what we eat, but when we eat that can lead to obesity. Calories eaten between meals or at strange hours are more likely to be stored as fat. 2

Dietitians can help their clients avoid this pattern by advising regular meal times with a balance of healthy carbs, fats, and protein. In addition, they should encourage clients to pay attention to hunger over habit and avoid eating just for the sake of eating. Snacks should ideally be nutrient-dense and include lean protein and/or fiber versus nutritional nothings like processed pastries or fried snacks, which may inevitably lead to overconsumption and weight gain. 

This research was funded by the National Institute of General Medical Sciences and University of Virginia Brain Institute. 

By Lisa Andrews, MEd, RD, LD


  2. Ryan M. Grippo, Qijun Tang, Qi Zhang, Sean R. Chadwick, Yingnan Gao, Everett B. Altherr, Laura Sipe, Aarti M. Purohit, Nidhi M. Purohit, Meghana D. Sunkara, Krystyna J. Cios, Michael Sidikpramana, Anthony J. Spano, John N. Campbell, Andrew D. Steele, Jay Hirsh, Christopher D. Deppmann, Martin Wu, Michael M. Scott, Ali D. Güler. Dopamine Signaling in the Suprachiasmatic Nucleus Enables Weight Gain Associated with Hedonic FeedingCurrent Biology, 2020; DOI: 10.1016/j.cub.2019.11.029
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