Timing physical activity to optimise health outcomes could be a powerful tool against obesity, so is it a new frontier or a passing fad?
It’s a perennial dilemma for exercisers: Is it better to hit the gym at first light or wait until the evening?
Obviously, it’s important to engage in some form of physical activity to ensure we give our bodies the best opportunity to fight disease and live a full and healthy life. However, it is not just a matter of how much we move, but also when we do it.
The time of day we exercise can help us get the best results to fight off the increasing number of obesity-related diseases.
Exercise has clear benefits on various functions that lead to a better quality of life, from managing liver fat stores, blood sugar levels, and cardiovascular health. That’s why, in clinical settings, exercise physiologists develop and prescribe different plans to suit your circumstances.
However, a lack of evidence has meant the timing of exercise is not part of the prescription.
That may be about to change.
Every day, our biological clocks tick to the beat of our circadian rhythms.
These rhythms play a critical role in regulating many physiological functions, including releasing hormones such as insulin, controlling your body temperature, sleep-wake cycles, and the all-important metabolism.
Exercising in the evening can have a greater effect on insulin sensitivity, which plays a key role in moving the transportation of glucose from the bloodstream to our cells where it is used to create energy.
Most healthy individuals can compensate for reduced insulin sensitivity by producing more insulin, which regulates their blood glucose levels. However, people with obesity and type 2 diabetes, cannot produce sufficient insulin to compensate for this day-night change in insulin sensitivity/resistance.
The chronic inability to effectively regulate glucose levels often leads to kidney and heart failure and, in many cases, causes premature deaths if not treated.
Like any clock, our biological clocks can become disrupted due to things like disease or a change in environment, and this can lead to metabolic abnormalities such as obesity and type 2 diabetes.
The risk of insulin resistance can, however, be altered through physical exercise. Given that physical activity, like nutrition, is a powerful regulator of metabolism and our biological clocks, some scholars proposed that these approaches can be used to “re-synchronise” our biological clock stemming from the fields of “chrono-nutrition” and “chrono-exercise“.
Recent clinical trials involving adults with type 2 diabetes or cardiovascular disease showed that exercising closer to the evening resulted in greater glucose control and blood pressure regulation than undertaking physical activity earlier in the day.
These clinical trials were conducted over a few weeks and months so, while it does remain unclear whether persistent habitual physical activity later in the day is associated with improved health outcomes and reduced risk of premature death, further study is required to cement the relationship between physical activity/exercise timing and health outcomes.
Our recent study published in Diabetes Care involving almost 30,000 participants, showed people with obesity who undertook regular bouts of moderate-to-vigorous intensity physical activity at any time significantly reduced the risk of developing cardiovascular complications such as heart failure, stroke, and kidney failure, as well as premature death.
Using data from wrist trackers and machine learning at Charles Perkins Centre’s Mackenzie Wearables Research Hub, researchers were able to capture participants’ regular physical activity patterns and classify them according to the time of the day they did the majority of their physical activity, including exercise.
The findings revealed that those who did most physical activity from 6pm to midnight experienced the lowest rates of mortality with a 61 per cent risk reduction and a 36 per cent cardiovascular disease risk reduction. These findings were even more pronounced in the subset of participants who, in addition to obesity, also had type 2 diabetes.
The results may be partly explained by the improved blood pressure and glucose regulation associated with undertaking physical activity during the evening, an explanation which is supported by recent clinical studies.
Our body is most insulin resistant at night, and for those who cannot produce more insulin to compensate, undertaking physical activity at this time may offset some of the evening-related insulin resistance.
Another important finding from our study was that the frequency of physical activity bouts was more closely associated with mortality than total volume.
This means that exercising more than once throughout the day or during specific time windows may be more beneficial than accumulating all your physical activity in one block.
This is supported by physiological evidence showing that repeated muscle contractions throughout the day may facilitate better blood glucose control, which ultimately reduces the risk of cardiovascular disease, organ failure, and other associated complications.
More research into “chrono-exercise” is needed to see just how crucial a role it could play in managing obesity-related conditions.
It is important to emphasise that physical activity undertaken at any time is beneficial for health. Once an active lifestyle is established, our results suggest that people, particularly those with obesity, may consider planning it during the evening to optimise its benefits.
Dr Angelo Sabag is a lecturer in exercise physiology at The University of Sydney’s Charles Perkins Centre and School of Health Sciences.
Dr Matthew Ahmadi is a National Heart Foundation Research Fellow at the University of Sydney’s Charles Perkins Centre in the Faculty of Medicine and Health and the deputy director of the Mackenzie Wearables Research Hub@CPC.
Professor Emmanuel Stamatakis is a Professor of physical activity and population health; an NHMRC Leadership 2 Fellow and director of the Mackenzie Wearables Research Hub@CPC.
This research was conducted using the UK Biobank resource under application 25813. This study was funded by an Australian National Health and Medical Research Council Investigator Grant (APP1194510) and the National Heart Foundation of Australia Postdoctoral Fellowship (APP107158).
Originally published under Creative Commons by 360info.
