We Decoded the Best Time To Work Out, According to Science

The most frustrating feeling in the world? Working out and feeling like you’re not making any progress. Yes, exercise takes time, but if you’re doing all the “right” things and still not seeing the results you want, there’s a good chance you’re doing one big thing wrong: not exercising at the optimal time of the day.

Believe it or not, timing may be everything when it comes to endurance, strength, muscle growth, weight loss, and all of the other benefits you’re hoping to reap from exercising. It seems that we’re hardwired for this because of our bodies’ circadian rhythms, which influence daily activities from sleeping to eating to—yep—exercising. On top of that, our chronotypes (whether we’re early birds or night owls) and our biological sex also play a role, since both influence body temperature, hormone levels, and preferred exercise times. 

“The combination of circadian rhythms and chronotype with the timing and mode of exercise appears to have a significant impact on the health and performance benefits we derive from the exercise,” says Paul Arciero, MD, a professor of Sports Medicine & Nutrition at the University of Pittsburgh and a professor of Health & Human Physiological Sciences at Skidmore College, who recently published some surprising data on this topic. “In our study of 50 men and women, we directly compared the physical and emotional performance benefits of exercising either early in the morning or evening—and we were surprised to find such a drastic difference between the groups, especially because they were all performing the exact same exercise routines during the 12-week study.” 

And that’s just one of the promising studies that indicate there’s an exact science to tailoring your workout by time and ultimately helping you work out smarter, not harder. So, what’s the best time to exercise? We’ve broken it down below based on various goals—and we’re not exaggerating when we say that this information just may change your life.

The Benefits of Morning Workouts

Rise and shine! If you’re looking to lose weight, target belly fat, and more, morning workouts are where it’s at, especially for women, according to Dr. Arciero’s research. So when that alarm goes off and you’re considering hitting the snooze button, remember that workout will be totally worth it.

Your Goal: Weight Loss and Reduced Belly Fat (Women)

Perhaps the most startling result of Dr. Arciero’s study was just how much more women responded to morning workouts between 6 a.m. and 8 a.m. when it came to these goals. “Specifically, women who exercise in the morning have much greater loss of total body fat (-5 percent vs. -2 percent) and belly fat (-10 percent vs. -3 percent),” says Dr. Arciero, who published these results in Frontiers in Physiology in 2022. Their blood pressure was also significantly reduced compared to women who performed the same workout at nighttime. (Men saw better results with these goals in the evening hours, which we’ll get into later.) 

Dr. Arciero details the optimal routine for weight loss and reducing fat in his book The PRISE Life, but here’s a brief overview: “I recommend for women to perform ‘intervals’ in the morning to optimize fat burning and then ‘resistance’ in the evening for ideal muscular performance and function.”

Your Goal: Sticking with an Exercise Routine

You know how it goes: You have the best intentions of exercising, but the later it gets, the more chances there are for that plan to go off the rails. You might have to work late, there might be tempting happy hour plans, the kids might have a bunch of activities, and you might just be exhausted after a long day. But in the morning, you don’t run the risk of life getting in the way, and studies show there’s a good chance you’ll be more consistent in exercising and creating good habits. According to a study of overweight individuals published in Exercise and Sport Sciences Reviews in 2020, morning workouts helped participants stick to their workout plans and lose weight. 

Perhaps since other data shows that women who work out in the morning lose more weight, these noticeable results further boost motivation and the desire to stick to it. While that hasn’t been scientifically proven, we can certainly see the allure and think, at least anecdotally, that there may be something to it.

Your Goal: Decreased Hunger

Morning exercise can act as a natural appetite suppressant. Morning workouts may make you less ravenous later in the day—or at least less tempted by pictures of mouthwatering food, according to one study in the journal Medicine and Science in Sports and Exercise in 2012. (Psst: Keep in mind that hunger is a natural cue from your body, so remember to tune into your needs and refuel after your workouts!) 

A more recent 2022 study by Stanford researchers may have figured out the reason for this phenomenon: an “anti-hunger molecule” (aka lac-phe, a hybrid of lactate and phenylalanine) released during certain types of exercise. While these scientists didn’t look at this molecule in relation to the best time of the day to exercise, it stands to reason that morning exercise could have a positive ripple effect on your appetite over the course of the day. One important thing to note: The intensity of your workout seems to be linked to how much lac-phe you produce—and how hungry you are afterward. That means you may need to work out at a higher intensity to achieve this effect.

The Benefits of Afternoon Workouts

If you can sneak out of the office in the middle of the day, your work might actually improve—and you just might improve your longevity. But if afternoon workouts are impossible, studies show that consistent exercise is still the most important factor when attempting to achieve any exercise goal. It’s all about creating and maintaining good habits with a routine.

Your Goal: Improved Heart Health and Longer Life

We all know that exercise can help us live longer—but these effects exponentially increase with an afternoon workout. A seven-year U.K. study of more than 92,000 men and women published in Nature Communications in 2023 found that people who worked out between 11 a.m. and 5 p.m. were less likely to die prematurely of heart disease or other causes (with the exception of cancer) than those who exercised outside that window. While this benefit was seen across the board in this study, benefits for men and the elderly were more pronounced.

Your Goal: Increased Focus and Brainpower 

The drudgery of your day can take its toll, and a midday workout can give your brain the break and boost it needs. “Several studies have shown that older adults who exercise in the afternoon tend to have better memory and reaction time following this exercise and more overall if the exercise is done routinely,” says Buman. One of these, a study published in the British Journal of Sports Medicine in 2020, showed afternoon exercise helped with working memory and executive functioning. 

“Exercise can promote brain neurogenesis (i.e., growth of new cells) and improve the function synapses between brain regions,” explains Matthew Buman, PhD, director and professor of Health Solutions at Arizona State University. “Since some older adults may have some decline in their cognition, we tend to see more pronounced effects of exercise in this group.” He adds that trained athletes who exercise at high intensities can show immediate cognitive benefits as well, though he’s quick to point out that everyone can benefit in this regard. “For many, the immediate events might not be noticeable, but over the long run, these benefits can prevent dementia and improve many other aspects of health,” Buman says, “and this is the case regardless of what time of day the exercise is performed.”

The Benefits of Evening Workouts

If you’re not a morning person or your mornings aren’t conducive to workout sessions, you might gravitate toward exercise later in the day. And that’s a particularly good thing for men looking to lose weight and improve their cholesterol levels, as well as men and women who want to build muscle. Hopefully that knowledge will motivate you when you’re thinking of an excuse to head straight to the couch instead of putting on your workout clothes.  

Your Goal: Weight Loss and Reduced Belly Fat (Men)

Remember how we said we’d get to the guys later in this story in relation to this goal? Well, here we are. According to Dr. Arciero’s study, men lost more weight and eliminated more fat when they worked out between 6:30 p.m. and 8:30 p.m. Just how much? Men burned 6 percent more fat in the evening hours compared to just 1 percent in morning workouts. Those nighttime workouts also lowered systolic blood pressure by 12 percent, as well as lowered cholesterol levels and feelings of fatigue. 

Your Goal: Strengthening Muscles

“There is substantial research showing that evening resistance training can promote greater muscle growth,” says Buman. “This is largely because the hormones that are released to build muscle are typically secreted during sleep, so timing resistance training in the evening can optimize muscle growth.” 

Dr. Arciero’s study backs this up. He found that evening exercise for women resulted in a significant increase in upper-body muscle strength (16 percent vs. 9 percent), power (37 percent vs. 8 percent), and endurance (40 percent vs. 25 percent) when compared to morning exercise. As a result, he recommends resistance training in the evening, with endurance and stretching routines that can also enhance sleep and help your body recover from morning fat-loss workouts.

Your Goal: Lowering Blood Sugar

If you have type 2 diabetes, pre-diabetes, or even simply deal with ricocheting energy levels and blood sugar spikes throughout the day, nighttime exercise may be your best bet, though exercising in the afternoon is a close second. In a study of overweight men and women in the Netherlands, published in the journal Diabetologia in 2022, researchers found that exercising between noon and midnight reduced insulin resistance as well as liver-fat content. Breaking it down further, exercising between 6 p.m. and midnight yielded a whopping 25 percent reduction in insulin resistance, while exercising between noon and 6 p.m. resulted in an 18 percent reduction. The ideal intensity? Moderate to vigorous. 

Beyond this, as the Cleveland Clinic notes, it’s important to keep the timing of your meals in mind if you have type 2 diabetes. They recommend exercising about 30 minutes after beginning your meal, referencing a 2017 study in Frontiers in Endocrinology. It’s also worth noting that after-dinner exercise has been shown to reduce triglyceride levels. 

Your Goal: Better Sleep

Conventional wisdom holds that working out too close to your bedtime will rev you up too much to have a good night’s sleep. Science, however, tells a different story. According to a recent study published in Sports Medicine, working out at night actually increases the amount of slow-wave sleep, the deepest type of sleep. This is “particularly [true with] high-performing distance runners and other endurance athletes who exercise later in the day or evening,” says Buman. “They have been shown to have more restorative sleep later that evening.” 

This might be about finding the sweet spot in your exercise: a moderate workout (think: a run, bike ride, or yoga session) that’s not too intense and ends at least an hour before you’re going to turn in. Because exercise releases endorphins and elevates your body temperature, your body needs a little time to return to normal before you drift off to dreamland. (You can also wind down with a sleep meditation.)

The Takeaway

Everyone has different exercise goals, and by finding the best time of day to work out, you just might be able to reach them faster and more efficiently. But while there may be a “best time” to exercise for those goals, the real key is to exercise consistently and, ideally, most days of the week. 

“For many, the most important factor to pay attention to is the time of day that will help you form a routine that you can stick with for the long run. There is certainly not a wrong time to exercise,” says Buman. “Exercise improves just about every organ and system in the human body, and this is the case regardless of the time of day. So find a time that works for you, and stick with it!”