Researchers at the University of Regensburg have investigated the relation between the diurnal timing at which people are physically active and the likelihood of obesity and diabetes. The results show that exercise in the afternoon and evening is particularly beneficial, while nocturnal activity was associated with a greater possibility of both common diseases.
Data from around 61,000 participants in the german National Cohort (NAKO) from 2015 to 2019 was analysed. The participants were given a movement sensor to measure their physical activity. This recorded their movements 24 hours a day over seven days. The researchers then divided the physical activity into time periods: morning (06:00-11:59), afternoon (12:00-17:59), evening (18:00-23:59) and night (00:00-06:00).
The team led by Michael Stein, a scientist at the University of Regensburg, used statistical methods to analyse the relation between the time of day of physical activity and the probability of obesity and diabetes. Obesity was defined as a body mass index ≥ 30. To diagnose diabetes, the researchers used either a doctor’s indication or the so-called HbA1c value. HbA1c is also known as long-term glucose and provides information on the average blood glucose level over the past two to three months. Parameters such as gender, age, study region, education, employment, alcohol consumption, smoking, night shift work and sleep duration were taken into account in the data analyses.
The results showed that the possibility of obesity and diabetes differed depending on the time of day of physical activity. A high level of physical activity in the afternoon and evening was associated with a lower probability of obesity than a high level of physical activity in the morning. Nocturnal activity had the least favourable effect on the likelihood of becoming severely overweight. The associations for diabetes were similar, with the lowest probability for afternoon activity, followed by evening and morning activity, and a higher probability for nocturnal activity. These associations remained even after adjusting for sleep duration, shift work and employment status.
“Studies have shown that the human metabolism follows a daily rhythm that influences insulin action and blood sugar levels. It could therefore be beneficial for people who are overweight or have diabetes to specifically schedule their physical activity in the afternoon or evening hours in order to synchronise the positive metabolic effects of physical activity with the metabolic rhythm. However, it must be emphasised that a single study can never provide concrete recommendations and that further studies are necessary in order to be able to make statements about causal relationships,” says first author of the publication Michael Stein. In addition, the present study did not differentiate between voluntary leisure-time activity and work-related exercise. The type of exercise – whether it was endurance or strength training – was also not determined. The study also did not take into account the participants’ diet, although this can influence the metabolism.
This study is a so-called cross-sectional study. This means that correlations were calculated on data from different people at one point in time. Longitudinal studies are an important prerequisite for investigating possible causes. This involves using data from the people studied at different points in time – for example from the baseline study and the second study of the NAKO participants. These research results then also make it possible to draw conclusions about the course of health.
Research with the NAKO
Scientists can currently use the data and biosamples from the baseline study (study period 2014-2019) of the NAKO for research purposes. The data from the second study (study period 2018-2024) will soon also be quality-assured and can be applied for by researchers via the TransferHub. With the data and biosamples from the baseline study and the 5-year follow-up, longitudinal studies will be possible in the future to investigate the progression and causal relation.
Originalpublication
Stein MJ, Weber A, Bamberg F, et al. Diurnal timing of physical activity in relation to obesity and diabetes in the German National Cohort (NAKO). Int J Obes. 2025. http://doi.org/10.1038/s41366-025-01721-9
Contact
Michael Stein
Lehrstuhl für Epidemiologie und Präventivmedizin
Universität Regensburg
michael.stein@ukr.de