In today’s busy world, many people stay up late, work overnight shifts, or spend hours in front of screens long after sunset.
These modern habits disrupt the body’s natural 24-hour rhythm—also known as the circadian rhythm—which controls when we sleep, eat, and function best.
A new scientific statement from the American Heart Association warns that disturbing this internal clock can seriously affect heart and metabolic health.
The report, published in the journal Circulation, outlines how poor circadian health may increase the risk of heart disease, obesity, type 2 diabetes, and high blood pressure.
Our circadian rhythm acts like a built-in timer, telling the body when it’s time to sleep, wake, digest food, and release hormones. This cycle repeats roughly every 24 hours and is guided mainly by light and darkness.
Light signals travel from the eyes to a small area in the brain called the hypothalamus, which then regulates hormones such as cortisol and melatonin.
Cortisol helps control stress and metabolism, while melatonin prepares the body for sleep. When we constantly change our schedule—by staying up late, eating at odd hours, or sleeping irregularly—this natural system gets thrown off balance.
Dr. Kristen Knutson from Northwestern University, who helped write the statement, explains that these interruptions are more than just mild annoyances.
She says that going to bed or waking up at the wrong time can trigger unhealthy changes in the body that raise the risk of heart and metabolic diseases. Aligning our daily habits with our internal clock, she says, is essential for maintaining good health.
Even small disruptions can matter. For example, many people experience what experts call “social jet lag.” This happens when sleep patterns differ between workdays and weekends.
You might stay up late and sleep in on your days off, then wake up early during the week. This inconsistency can confuse your body clock, leading to higher risks of obesity, diabetes, and poor metabolic control—even if you get enough total hours of sleep.
Light exposure also plays a big role. Getting morning sunlight helps the body’s rhythm stay on track, while bright light at night—especially from phone and computer screens—can suppress melatonin and delay sleep. Even small amounts of nighttime light exposure have been linked to an increased risk of heart disease.
The timing of meals can also affect your body clock. Eating late at night or skipping breakfast may throw off the internal timing of organs like the liver and pancreas, which help regulate blood sugar and metabolism. Studies suggest that eating earlier in the day, such as before 8 a.m., can help lower the risk of type 2 diabetes and improve overall heart health.
Exercise, too, influences circadian rhythms. Working out in the morning or afternoon may help your body stay aligned with its natural cycle, while exercising late at night could delay your internal clock.
More research is needed to confirm the best time to exercise for heart health, but regular activity at consistent times seems to support better sleep and blood pressure control.
Certain groups, such as night shift workers, face even bigger challenges. People who work irregular hours are often exposed to light at the wrong times, eat meals late, and struggle with inconsistent sleep patterns.
This kind of chronic disruption increases the risk of heart disease, obesity, and other health problems. Light pollution from cities can make these effects worse, especially when people never experience true darkness at night.
The American Heart Association emphasizes that each person’s internal clock is unique. Some people are naturally early risers (“morning types”), while others feel more alert later in the day (“night owls”). Recognizing your natural rhythm and adjusting your schedule accordingly may improve both your physical and mental health.
In the future, wearable technology and artificial intelligence may make it easier for doctors to measure and monitor circadian rhythms in daily life, helping tailor health advice to each individual.
The statement encourages simple changes that anyone can make—such as keeping a regular sleep schedule, eating meals earlier, exercising at the same time every day, and getting morning sunlight. Dr. Knutson adds that listening to your internal clock isn’t just about getting better sleep—it’s about protecting your heart, metabolism, and overall well-being.
In reviewing the study, it’s clear that our bodies depend on regular rhythms to stay healthy. Disruptions caused by irregular sleep, late-night eating, or lack of sunlight may seem harmless but can slowly wear down heart health and metabolic balance.
The message is simple but powerful: consistency matters. Aligning your habits with your natural body clock could be one of the easiest and most effective ways to support long-term heart and metabolic health.
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The study is published in Circulation.
