American College of Cardiology Annual Scientific Session, March 2026 | Prem Patel et al., University of Massachusetts Chan Medical School | All of Us Cohort
People who exercised regularly between 7 a.m. and 8 a.m. had the lowest odds of coronary artery disease in a large new study-and morning exercisers broadly outpaced later movers across every major cardiometabolic marker measured.
Researchers analyzed health records and Fitbit-derived heart rate data from 14,489 participants in All of Us, a large national study. Rather than tracking specific activities, the methodology captured elevated heart rate sustained for 15 or more consecutive minutes—a measure of the body’s actual response to effort. Data collection ran for a full year, giving researchers an unusually detailed picture of real-world exercise behavior.
The risk differences were substantial. Compared to those who exercised later in the day, consistent morning movers were 31% less likely to have coronary artery disease, 30% less likely to have type 2 diabetes, 35% less likely to have obesity, and 18% and 21% less likely to have high blood pressure or elevated cholesterol, respectively. Those associations held true independent of total daily activity volume-meaning the timing carried weight beyond simply how much people moved.
“Any exercise is going to be better than no exercise,” said Patel, adding, “If you can exercise in the morning, it seems to be linked with better rates of cardiometabolic disease.”
The study is observational, and the mechanism isn’t yet established. Researchers point to circadian biology, morning hormonal rhythms, and the downstream effect of early exercise on energy and food choices as leading candidates. But what the data suggests is that the timing is not incidental.
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