Millions of Americans cut time out of their busy schedule to exercise daily. However, only 23% of adults aged 18+ meet the recommended guidelines for both aerobic and muscle-strengthening activity. The biggest obstacle for most people: Not having enough time. On the contrary, says a study from 2019 from CDC and Rand. The survey of more than 30,000 participants showed that Americans on average have more than five hours of free time a day.
Whether you’re considering starting an exercise program or a more experienced athlete, one of the biggest questions I hear is, “When is the best time to exercise?” Most people are quite regimental and protective when exercising. Choosing to exercise in the morning or evening is often a product of a work schedule or childcare responsibilities. Or just whether you are a “morning person” or a “night owl”.
But is there any science that supports training in the morning compared to training in the evening? A recent research study in Frontiers in Physiology shed some light.
Are you next? More Americans than ever are being diagnosed with high blood pressure.
More:Are you at risk for a heart attack during your workout?
The early bird gets the training worm?
This was a relatively small study from Skidmore University that collected data from 27 women and 20 men who were already very active with a regular exercise regimen. Participants were followed over 12 weeks. They did one of four different training routines – stretching, resistance training, interval sprints or endurance training – four times a week for one hour each time. One group did the routine between 6:30 and 8:30 and the other group between 6 and 8 p.m.
For the group that trained in the morning:
- Women had a 7% greater loss of belly fat, greater reduction in blood pressure and greater bone strength
For the group that trained in the evening:
- Women had a greater increase in upper body strength, power and endurance and mood improvement
- Men had improved heart health, metabolic health and emotional well-being
- Men also had a greater weight loss and reduction in blood pressure
Dive deeper into other research
Previous studies examining the time-dependent effects of exercise were inconsistent with the results of this new study. In contrast, a small study from 2019 found that men also had greater weight loss if they exercised in the morning. However, several previous studies support the current study result of improved metabolic health in men who exercised in the afternoon, including better insulin sensitivity and blood sugar control.
In January 2022, an international consortium of researchers conducted a fascinating research study that looked at the molecular changes that occur in the cells of several organs in mice to try to quantify at the most basic cellular level what happens when exercising in the morning versus in the evening. . The molecular profiles in mice showed a greater dependence on fat to nourish morning exercise and a greater dependence on glucose to nourish afternoon exercise. While some might argue that we can not extrapolate data about mice to humans, the cellular processes at the molecular levels are similar.
Does TikTok’s ‘pomegranate pump’ actually work? The answer may surprise you
On social media, people drink a gallon a day … How much water do you really need?
Additional factors that have been thought to play a role include sleep quality and hormones.
The role of sleep
One possible explanation is that women tend to spend more time in the deep sleep stage and therefore tend to be more attentive and ready to exercise earlier in the morning. But there are plenty of men who also prefer to exercise in the morning. This brings us to one of the biggest myths about sleep and exercise; that exercising late at night or close to bedtime will lead to reduced sleep quality. Again, it depends. Exercising late in the day may not affect your self-described night owls. And most importantly, a meta-analysis identified 29 studies that showed that exercise improved sleep quality or duration.
Do not count hormones
Levels of cortisol, the stress hormone, vary higher for both men and women in the morning. This can generate a need to “burn off” stress for both men and women who prefer to work out cardio-like earlier in the morning. However, cortisol can have an inhibitory or catabolic effect on muscle building. So men and women whose goal is strength training may see greater benefits from evening training.
Also worth mentioning is that the latest study found that macronutrient intake did not play a role. Study participants were also required to adhere to the same exact eating regimen for foyer meals a day at the same times for 12 weeks.
The ‘X’ factor: You do
Bottom line: This was a small study, and there’s still a lot we do not know about the time-dependent benefits of exercise. This adds to the evidence that the metabolic benefits are higher for men who exercise in the evening. For women whose goal is to burn fat, this study showed a clear benefit of a morning workout. And I think we can not ignore the catabolic effects of cortisol; for men and women whose goal is to build strength, an evening workout may be preferable.
Whether you exercise in the morning or in the evening, the key point is that you exercise and definitely reap its many benefits. If you feel better mentally and enjoy exercising early in the morning, then keep at it! If you have a specific goal in mind, consider the results of the surveys when choosing your time of day to exercise.
Can daily coffee use prolong your life? Here’s what the latest research says
Michael Daignault, MD, is a board-certified emergency physician in Los Angeles. He studied Global Health at Georgetown University and holds a medical degree from Ben-Gurion University. He completed his residency in emergency medicine at Lincoln Medical Center in the South Bronx. He is also a former volunteer in the United States Peace Corps. Find him on Instagram @ dr.daignault