A large study using Fitbit data suggests that breaking a sweat early in the day is linked with lower rates of heart disease and other metabolic conditions, even after accounting for how much people move overall.
Setting your alarm a little earlier to work out might do more than free up your evenings. It could also be linked with a healthier heart and metabolism.
People who regularly exercised early in the morning were significantly less likely to have coronary artery disease, high blood pressure, Type 2 diabetes or obesity than people who tended to exercise later in the day, according to new research being presented at the American College of Cardiology’s Annual Scientific Session (ACC.26).
The study drew on health records and Fitbit-derived heart rate data from more than 14,000 adults participating in All of Us, a large national research program. Researchers say the findings highlight exercise timing as a potentially important, and often overlooked, piece of the heart-health puzzle.
Lead author Prem Patel, a medical student at the University of Massachusetts Chan Medical School, noted the team wanted to go beyond the usual advice that simply focuses on moving more.
“Any exercise is going to be better than no exercise, but we tried to identify an additional dimension relating to the timing of exercise,” Patel said in a news release. “If you can exercise in the morning, it seems to be linked with better rates of cardiometabolic disease.”
Cardiometabolic conditions, such as high blood pressure, diabetes, obesity and abnormal cholesterol, are major risk factors for heart disease, the leading cause of death worldwide. Decades of research show that regular physical activity can lower these risks and help prevent heart attacks and strokes. But most guidelines and past studies have focused on how much and how hard people should exercise, not when they should do it.
This new work takes advantage of the rise of wearable devices to look at exercise patterns in much finer detail than was possible before.
Researchers analyzed minute-by-minute heart rate data from Fitbit devices worn by 14,489 people over the course of a year. Instead of asking participants to recall their workouts or tracking specific activities like walking to work or going to the gym, the team looked for periods when a person’s heart rate was elevated for at least 15 consecutive minutes. Those stretches were counted as bursts of physical activity, capturing the body’s response rather than the type of movement.
They then mapped those activity bursts across the day in 15-minute intervals and grouped people based on when they tended to be most active. Using participants’ electronic health records, the researchers compared rates of high blood pressure, diabetes, obesity and high cholesterol, as well as cardiovascular outcomes such as coronary artery disease and atrial fibrillation, across the different timing groups.
Importantly, they adjusted for a wide range of other factors that affect heart health, including age, sex, income, total activity level, sleep duration, alcohol use and smoking status.
Compared with people who usually exercised later in the day, those who frequently worked out in the morning had:
- 31% lower odds of coronary artery disease
- 18% lower odds of high blood pressure
- 21% lower odds of hyperlipidemia (elevated LDL cholesterol or triglycerides)
- 30% lower odds of Type 2 diabetes
- 35% lower odds of obesity
These links held even after accounting for how much total physical activity people got each day. In other words, among people who moved similar amounts overall, those who tended to be active earlier in the day had better cardiometabolic profiles.
Exercise between 7 and 8 a.m. was tied to the lowest odds of coronary artery disease.
The study cannot prove that morning exercise directly causes these health benefits. It only shows an association. Patel and colleagues say several biological and behavioral factors could be driving the pattern.
Hormones that influence blood sugar, blood pressure and fat metabolism follow daily rhythms, and early exercise might interact with those rhythms in beneficial ways. Sleep patterns and genetics could also play a role. On the behavioral side, people who work out first thing may be more likely to make healthier choices throughout the day, such as eating more nutritious foods or avoiding late-night snacking. Morning exercisers might also be more consistent, since they get their workout in before work, classes or family responsibilities can interfere.
More research is needed to tease apart these possibilities and to see whether shifting exercise to earlier in the day can improve health for people who currently work out later.
Even so, the study offers a new way of thinking about daily movement, made possible by the widespread use of fitness trackers and smartwatches.
“In the past, researchers have mainly looked at how much physical activity to do, the number of minutes or the intensity of physical activity,” Patel added. “Now with 1 in 3 Americans having a wearable device, we’re gaining the ability to look at exercise at the minute-by-minute level, and that opens a lot of doors in terms of new analyses.”
Unlike short-term lab experiments, this analysis captured real-world behavior over an entire year. That long view allowed the team to see consistent patterns in when people moved and how those patterns related to long-term health markers.
For students and busy professionals, the findings may offer both motivation and flexibility. If early mornings are realistic, carving out time to walk, run, cycle or do a quick strength routine before the day starts could bring extra benefits beyond simply checking the exercise box. For those who truly cannot manage morning workouts, experts still emphasize that moving at any time of day is far better than not moving at all.
The researchers plan to continue exploring how exercise timing interacts with other lifestyle factors and whether tailored advice based on a person’s daily rhythms could help prevent or manage cardiometabolic disease.
The study, titled “Exercise Timing and Relationship with Cardiometabolic Disease,” will be presented March 29 at ACC.26 in New Orleans, where cardiologists and cardiovascular specialists from around the world will gather to share new discoveries in prevention and treatment.
For now, the message is straightforward: keep moving, and if your schedule allows, consider setting that alarm a bit earlier. Your heart and metabolism may thank you.
Source: American College of Cardiology