According to a recent study published in the International Journal of Cancer, those who regularly exercised in the morning (between 8 a.m. and 10 a.m.) had a lower risk of developing cancer, especially breast and prostate cancer.
This is due to the fact that exercising later in the day can mess with your body’s circadian rhythm—disrupting it regularly can up your risk of certain health conditions, like cancer.
Morning exercise, however, can help reset your body clock and lower health risks (like cancer) as a result.
Morning workouts come with a some notable perks: They can give you the energy you need to jumpstart your day, and they may help you sleep better at night, to name a few. Here’s one more reason to motivate yourself into an a.m. run: You could be lowering your risk for certain types of cancers.
Researchers looked at 2,795 participants in an ongoing study in Spain that tracks the influence of environmental and genetic factors in cancer prevention—especially colorectal, breast, gastroesophageal, and prostate cancers, as well as chronic lymphocytic leukemia.
In results published in the International Journal of Cancer, they found that those who regularly exercised in the morning (between 8 a.m. and 10 a.m.) had reduced cancer prevalence, especially for breast and prostate cancer. The protective effects of early morning exercise were more pronounced for those who naturally preferred to work out in the afternoon or evening (called an intermediate or evening chronotype). The reason for this may be related to the timing of physical activity on “sex steroid production.”
For example, higher levels of oestrogen are associated with increased breast cancer risk, researchers state. Production of estradiol—a main oestrogen hormone—peaks around 7 a.m., but physical activity can lower oestrogen levels. That means morning workouts can keep estradiol levels more regulated.
Your chronotype is based on when you prefer to be active during the day. Many researchers, like those in the recent study, break these down into three standard types—morning (preference to be active in the mornings), intermediate (preference to be active in the afternoons), and evening (preference to be active in the evenings).
No matter which type you are, there can be disruption in your circadian rhythm, and that’s been linked in the past to increased cancer risk, as well other major problems like cardiovascular disease and diabetes.
A solid sleep schedule helps reduce your risk of these health concerns, but as this study also points out, morning exercise can also help reset your body clock and lower health risks (like cancer) as a result.
This research is part of a larger trend within the past couple years on the effects of circadian rhythm for health outcomes, with a particular focus on exercise’s role.
For example, a study published last year in The Journal of Physiology found that exercise at 7 a.m. or between 1 p.m. and 4 p.m. advanced the body clock enough that people were able to start activities earlier the next day. By contrast, exercising in the evening between 7 p.m. and 10 p.m. delayed the body clock, which means they had a harder time getting to peak-performance mode until later the next day.
The coauthor of that study, Shawn Youngstedt, Ph.D., a professor at Arizona State University’s College of Nursing and Health Innovation, told Runner’s World that the reason for this may be tied to how exercise improves hormone regulation, which affects a wide range of physiological functions—from your sleep-wake cycle to fat storage, anxiety, pain management, blood pressure, appetite, and mood.
'As you improve your hormone regulation, your body clock will become more efficient, and that has a huge ripple effect on your health,' Youngstedt said. 'Like many researchers, we found exercise is key in this process, and its benefits for preventive health are significant.'
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