Every spring and fall, Americans still go through the strange ritual of turning their clocks forward one hour and then back one hour. It feels harmless and is only a temporary interruption. But more and more research shows that these ongoing changes may be causing more damage than we think. In addition to lack of sleep, you are at higher risk for obesity, heart problems, and even stroke. The simplest solution is to stop the transition time completely.
clock built into the body
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Our bodies operate according to a 24-hour internal rhythm known as the biological clock. It controls when we are awake, tired, hungry and ready to rest. Every spring, when Daylight Savings Time (DST) begins, we “lose” an hour of morning sunlight. The change may not seem like much, but it changes the way our bodies synchronize with natural light. According to Stanford researchers Lara Weed and Jamie Zeitzer, these changes disrupt the body’s internal timing system, affecting metabolic and cardiovascular health.
Their study, published in the Proceedings of the National Academy of Sciences, compared permanent standard time, permanent daylight saving time, and the current twice-a-year transition to see how each affects circadian alignment. Data shows that keeping a consistent schedule is healthier overall, with permanent standard hours being the best option. It provides more morning light, helping your body stay in sync with natural light and reducing what scientists call circadian “jet lag.” Other countries, such as Mexico, have already suspended seasonal clock changes to support public health and productivity.
The hidden weight of time change
The Stanford team found that adopting permanent standard time could reduce obesity nationally by about 0.78 percent, resulting in 2.6 million fewer obese people. This could also mean about 300,000 fewer strokes each year. Permanent daylight saving time would still be beneficial, but to a lesser extent, with an estimated 1.7 million fewer cases of obesity and 220,000 fewer strokes.
Morning sunlight helps regulate appetite hormones, sleep quality, and insulin response, which all affect weight. Without sufficient exposure to light early on, our internal clocks can drift later in life, disrupting our metabolism and energy levels. Over time, this misalignment contributes to weight gain even for people who maintain a stable diet and exercise routine. The study found no significant effects on other conditions such as diabetes, arthritis, or depression. This suggests that the timing of light exposure plays a greater role in metabolic and cardiovascular health than in other areas.
Why the Clock Wars Continue
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Even if science favors standard time, there is still disagreement about which policy should become permanent. Supporters of permanent daylight saving time argue that more evening light saves energy and provides more daylight for people after work. The United States tried this approach during the 1974 energy crisis, but complaints about dark mornings and school safety concerns led to the experiment being halted after a year.
Instead, health organizations strongly support standard time. The American Medical Association, American Academy of Sleep Medicine, and National Sleep Foundation all agree that morning sunlight promotes healthier sleep patterns and better metabolic function. Zeitzer said this new data provides concrete evidence for what experts have suspected for years. That means our bodies actually work better the earlier they are exposed to sunlight.
Changing our clocks twice a year may seem harmless, but it’s wreaking havoc hidden within our bodies. Each shift disrupts the way our internal clock synchronizes with the environment, and these minor disturbances accumulate over time.
Maintaining consistent hours throughout the year won’t add more daylight, but it will give our bodies a better opportunity to naturally adapt. After all, our health simply depends on what we eat and how we move. It also depends on the light in which we wake up.
