Alex Eben Meyer
The numbers are stark. In the 1970s, approximately 13 percent of American adults and 5 percent of children had obesity. By 2020, those figures were over 41 percent for adults and 19 percent for children aged 2 to 19.
That drastic shift in only 50 years is related to the modern American food environment, in which ultra-processed, high-fat, and high-sugar foods abound and are often the easiest to access, says Dana Small, a professor of psychiatry and psychology. Consuming those foods over time, according to a study by Small, colleagues at Yale, and Germany’s Max Planck Institute, can rewire the brain—creating a shift in eating preferences away from healthier foods. The study was published in Cell Metabolism.
The researchers divided 49 healthy people into two groups. One group received two high-fat, high-sugar snacks daily for eight weeks, while the other received a low-fat, low-sugar, higher-protein version. The calorie count of the snacks was the same and participants continued their usual eating habits.
At the end, participants rated foods with varying fat contents and sugar levels. Those who had eaten the high-fat, high-sugar snacks did not like low-fat and low-sugar options as much as they had at the start. Next, participants underwent MRI scans while drinking milkshakes. The scans showed increased activity in the brain’s reward circuits for the high-sugar, high-fat group, but not for the other.
Small says this is “the first study to show that dietary changes in themselves can rewire humans’ brain circuitry—similar to the working of addictive drugs—and increase the long-term risk of overindulgence in unhealthy foods.”
That knowledge, she says, means that obesity and diet-related health problems such as diabetes and cardiovascular disease cannot be solved with individual willpower. “We have to do better at creating healthier food environments, especially for kids. Habitual early exposure to high-fat, high-sugar processed food is a critical driver of lifetime eating habits.”
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