Doing away with switching the clocks for daylight savings twice a year could prevent millions of cases of obesity and hundreds of thousands of strokes, according to a new study from Stanford University School of Medicine.

Switching between daylight saving time, or the “spring forward” period, and standard time, or the “fall back period,” significantly affects the body’s natural circadian rhythms, which regulate sleep and our long-term health.

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Study authors Jamie Zeitzer, professor of psychiatry and behavioral sciences, and graduate student Lara Weed, conducted their study with funding from the National Institutes of Health’s Center on Sleep Disorders Research and published their findings on Monday in the academic journal Proceedings of the National Academy of Sciences. 

Zeitzer and Weed used mathematical modeling to translate light exposure based upon sunrise and sunset times under daylight saving time and standard time to circadian burden, or how much a person’s internal clock needs to shift to keep up with a 24-hour day.

Using data from the Centers for Disease Control and Prevention, the researchers modeled the time-switching effects on circadian rhythms for various chronic diseases, including heart disease, diabetes, and obesity. 

Their model found that implementing a permanent standard time, or the “fall back” time, would reduce the number of cases of obesity by 2.6 million and the number of strokes by roughly 300,000. 

Implementing a permanent daylight saving time model, or the “spring forward” time, would only decrease obesity by 1.7 million people and prevent roughly 220,000 strokes. 

“The more light exposure you get at the wrong times, the weaker the circadian clock. All of these things that are downstream — for example, your immune system, your energy — don’t match up quite as well,” Zeitzer said in a university press release.

The authors noted that the negative health consequences of the “spring forward” time change are already well documented. These included an increased risk of heart attack and car crashes, as well as decreases in sleep and work engagement. 

The “fall back” zone of standard time does not demonstrate these effects. 

President Donald Trump called on Congress this spring to adopt a permanent daylight saving time structure, saying in a Truth Social post that it’s “very popular” and calling changing the clocks “a big inconvenience.”

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Senate Commerce Committee Chairman Ted Cruz (R-TX) said at the time that there is a broad consensus in Congress to end the practice of switching the clocks twice annually, but the debate has been about what time should be the new standard.

In 2022, the Senate unanimously passed legislation introduced by then-Sen. Marco Rubio (R-FL) to create a permanent daylight saving time, but the legislation died in the House.