Early morning workouts linked to lower obesity risk, study finds

New research suggests exercising earlier in the day may play a key role in reducing obesity and improving overall metabolic health

People who exercise early in the morning may be significantly less likely to develop obesity and other cardiometabolic conditions, according to new research presented at the American College of Cardiology Annual Scientific Session ACC.26.

The study, led by Prem Patel of the University of Massachusetts Chan Medical School, analysed health records and wearable device data from more than 14,000 participants. Findings indicate that individuals who consistently exercised earlier in the day had markedly lower rates of obesity, alongside reduced prevalence of conditions such as type 2 diabetes and high blood pressure.

Compared with those who exercised later in the day, morning exercisers were 35 per cent less likely to live with obesity. They were also 30 per cent less likely to live with type 2 diabetes and showed lower rates of other cardiometabolic risk factors, including high cholesterol and coronary artery disease. Exercise between 7:00 and 8:00 a.m. appeared to be associated with the most favourable outcomes, particularly in relation to heart health.

Although physical activity at any time of day remains beneficial, the findings suggest that timing could play a meaningful role in obesity risk and metabolic health.

The research drew on data from the All of Us Research Programme, incorporating minute-by-minute heart rate readings from Fitbit devices over a one-year period. Instead of tracking specific activities, researchers identified sustained periods of elevated heart rate lasting at least 15 minutes to capture meaningful bouts of exercise.

Participants were then grouped according to when they most frequently exercised, allowing researchers to examine links between exercise timing and conditions including obesity, high blood pressure and cardiovascular disease. Importantly, the associations remained even after accounting for factors such as age, sex, income, sleep, smoking and total daily activity levels.

Researchers caution that the findings show association rather than causation. Biological factors such as hormones, sleep cycles and genetics may influence the relationship, while behavioural patterns could also play a role. For example, people who exercise early may be more likely to maintain healthier routines throughout the day.

Nevertheless, the study highlights how wearable technology is enabling more detailed analysis of lifestyle behaviours, opening new avenues for personalised obesity prevention strategies.