Morning Exercise Linked to Lower Cardiometabolic Risk: Study Findings

A preliminary study presented at the American College of Cardiology (ACC26) Annual Scientific Session suggests that regular morning exercise is associated with a reduced risk of cardiometabolic disease. The research, based on health records and heart rate data from Fitbit devices worn by over 14,000 individuals, identified significant correlations between exercise timing and health outcomes.

Researchers analyzed minute-by-minute data from 14,489 participants in the ‘All of Us’ research program, a large-scale national study in the United States. They defined periods of physical activity as 15 consecutive minutes or more with elevated heart rates. Participants were then categorized based on the time of day they engaged in exercise.

The study found that individuals who consistently exercised in the morning demonstrated a 31% lower likelihood of developing coronary artery disease compared to those who exercised later in the day. The morning exercise group exhibited an 18% reduction in the risk of hypertension, a 21% decrease in the probability of hyperlipidemia, a 30% lower chance of being diagnosed with type 2 diabetes and a 35% reduction in the risk of obesity.

Notably, these associations remained consistent regardless of the total daily amount of physical activity. The strongest benefits were observed with exercise performed between 7:00 and 8:00 a.m., correlating with the lowest probabilities of coronary artery disease.

“Any exercise is better than no exercise, but we were trying to identify an additional dimension related to the timing of exercise,” explained Prem Patel, a medical student at the University of Massachusetts Chan Medical School and the study’s lead author. He emphasized that the findings demonstrate an association, not necessarily causation, and that biological, behavioral, and psychological factors could contribute to the observed relationships.

Researchers state This represents the first large-scale study to evaluate both the quantity and timing of exercise using long-term data from wearable devices. Fitbit devices utilize a three-axis accelerometer to count steps and determine the frequency, duration, intensity, and patterns of movement, according to Fitbit’s support documentation. The devices also calculate distance based on stride length, which is estimated based on height and sex, or through GPS data when available.

The study’s findings build on existing recommendations for regular physical activity, but suggest a potential benefit to prioritizing exercise earlier in the day. Further research is needed to determine the underlying mechanisms driving these associations and to establish definitive causal links.