If you exercise at lunchtime, there may be moments — possibly when you're unpacking the sweaty clothes from your gym bag each evening — when you wonder if it’s worth the trouble. But the findings of a new study of more than 90,000 people may inspire you to keep fighting the good fight: Working out in the afternoon reduced the risk of early death more than physical activity in the morning or afternoon.
The study, published February 18 in Nature Communications, provides good evidence that a nonmedication intervention such as physical activity makes a difference in health outcomes, says Fatima Z. Syed, MD, an associate professor of medicine and a physician at Duke Lifestyle and Fitness Center in Durham, North Carolina, who was not involved in the research.
“The study ultimately shows that doing moderate to vigorous activity (MVPA) is associated with a lower likelihood of dying from cardiovascular disease or cancer. I think this tells us it's not just about weight, but also about moving for overall health,” says Dr. Syed.
But Syed is concerned that people may read the headlines and think that if they can’t exercise in the afternoon, then exercising at other times in the day is not as valuable. “That is absolutely not the case. I interpret these findings to show that exercise itself is worth it, and if you can do that in the afternoon, even better,” she says.
Moderate to Vigorous Exercise Reduced the Risk of Death From Any Cause, Heart Disease, and Cancer
To examine the relationship between exercise, exercise timing, and the overall risk of death, as well as death from specific causes, researchers used health and demographic data from about 92,000 people in a United Kingdom biomedical database.
All participants wore an accelerometer for a week, which tracked the time of day they exercised and how hard they worked out.
After gathering that data, investigators placed participants into one of four groups according to when they exercised:
- Morning, from 5 a.m. to 11 a.m.
- Afternoon, from 11 a.m. to 5 p.m.
- Evening, from 5 p.m. to midnight
- A group that didn’t show a time preference and exercised at different times of day throughout the week
After an average of 7 years, the investigators checked the death records of the participants. A total of 3,088 (3.4 percent) participants had died; 1,076 (1.2 percent) had died of heart disease; and 1,872 (2 percent) had died of cancer.
Afternoon Exercisers Had a Lower Risk of Early Death Than Morning or Evening Exercisers
The authors found that moderate to vigorous exercise any time of day was better than no exercise in reducing the risk of death from any cause, heart disease, and cancer.
But the effects weren’t equal for everyone. People who worked out in the midafternoon and people who regularly changed their exercise time from day to day had a lower risk of death, both in general and from heart disease, than evening and morning exercisers.
The findings suggest that exercise timing may have the potential to maximize the health benefits of daily physical activity, the authors concluded.
“The overall findings from this very large study align with what we know: The more you move, the healthier you are. It validates what we’ve been trying to get people to do for a long time,” says Laura Richardson, PhD, a clinical associate professor of applied exercise science and movement science at the University of Michigan in Ann Arbor. Dr. Richardson was not involved in the new research.
These findings also provide additional insight as to the ideal time of day for the majority of people to engage in MVPA for a longer life, says Paul Arciero, a doctor of exercise physiology and a professor in the health and human physiological sciences department at Skidmore College in Saratoga Springs, New York, and the author of the book The Protein Pacing Diet.
“Intuitively, it makes sense that midday exercise reduces the risk of heart disease death and [death from] other causes,'' says Dr. Arciero, who was also not involved in the new study. Vigorous physical activity performed early in the morning is known to increase the chances of a cardiovascular event such as a heart attack or stroke compared with exercise at other times of the day, and evening exercise can cause sleep disturbances that may adversely affect the heart, he adds.
Who Benefits the Most From Afternoon Workouts?
The lowered risk of heart disease death with afternoon workouts was especially strong among men, the elderly, less active individuals, and people with preexisting heart disease, noted the authors.
“That’s an interesting finding and aligns with what I see in my practice,” says Dr. Anderson.
“When we look at people who were in that midday group — people who were out of shape, the elderly, those that are already identified as having less activity — in my experience, those people often prefer midday exercise,” says Anderson.
People who are retired or who have existing heart issues or obesity often choose afternoon exercise because that’s when they feel the best, she explains. “They’ve had their breakfast, taken their medicine, their bodies are not as achy.”
Circadian Rhythms May Be Linked to Why Afternoon Exercise Provides Greater Benefits
Although the study was not designed to discover why exercise timing could influence early death, the authors of the study believe that it could be linked to our bodies’ circadian rhythms, which are the physical, mental, and behavior patterns that follow a 24-hour cycle.
Circadian rhythms could be the key, says Syed. “We have peaks in blood pressure and other hormones like cortisol in the morning, and similar peaks happen at bedtime. Maybe we are meant to be our most physically productive outside of those peaks,” she says.
By the afternoon, the body has had time to sufficiently adjust to the day, says Arciero. “Our metabolism peaks in the afternoon; the heart, blood vessels, hormones, muscles, joints, and nervous system are also working at optimal form, and we are usually well-nourished by this time,” he says.
That would make the afternoon the most favorable time of day to perform vigorous exercise, because all these processes are working at their best, says Arciero.
Morning Exercise May Be More Effective for Burning Fat
Although certainly the largest, this study isn’t the first to suggest that the health benefits of exercise may depend on timing. A study published in the December 2020 Physiological Reports found that people who were at risk for or diagnosed with type 2 diabetes improved their blood-sugar control more if they worked out between 3 p.m. and 6 p.m. than if they exercised in the morning.
Exercise timing may also influence how our body burns energy and builds muscle. In a small study published in the May 2022 Frontiers in Physiology, Arciero and his colleagues found that early-morning exercise in women reduced total body and belly fat and increased the lower body muscular power of their legs. Evening exercise in women significantly increased upper body strength, power, and endurance.
In men, evening exercise increased fat oxidation and decreased fatigue. “Other research has shown similar enhanced fat burning following morning exercise and improved athletic and exercise performance with late afternoon or evening exercise,” says Arciero.
Bottom Line: Exercise at Whatever Time of Day Fits Your Lifestyle
All the experts agree: The best time to exercise is when you can fit it in.
“Based on this article, in an ideal world would midafternoon vigorous exercise be best? Sure. Is that possible for my patient who has meetings all afternoon and only has a window to exercise after the kids go down? No. Is it possible for the patient who does shift work and needs to sleep during the day? No. But if a patient has space for flexibility, I would say, the best time to exercise for all its maximum benefit is in the afternoon,” says Syed.
Tips for Moving More in the Afternoon
Rule number one? Exercise does not need to be structured, says Syed. “Just get moving. Take the stairs during your lunch breaks, take a Zoom call while doing a brisk walk, have a midday dance party with the kids. Do what you can, and all of it counts,” she says.
Arciero recommends a 10- to 15-minute power walk in the office stairwell or a loop around the neighborhood. If you can’t leave your desk area, body weight lunges and resistance bands can provide a little burst of activity and get your heart rate up, he says.