There’s always been debate about the best time of day to work out. I’ve always heard that exercising first thing in the morning is ideal, but others say a nighttime workout benefits them more. But is one time really better than another, and why?

Regardless of when you work out, there are many health benefits from moving regularly, like improving your heart health, getting stronger or even improving your endurance. Most people decide to exercise when it best fits their schedule, so oftentimes they can’t help the time of the day they choose to be active.

Research has shown, however, that the time of day you choose to exercise can affect your workout in various ways. Here’s how to determine what’s best for you based on the latest data.

The best time to exercise is whenever you can 

Let’s get this out of the way first: The best time to work out is whenever you can. We don’t all have schedules that allow for a 90-minute workout, green smoothies with collagen and a 20-minute session with a Theragun, unfortunately. 

If your only time of day to exercise is before work, then morning is best. If you reserve physical activity for packed evenings, there’s a good chance you won’t ever get to it. 

Likewise, if you can only squash 20 minutes of exercise into your day right before you get ready for bed, that’s the best time to work out. 

I want to add a note on consistency, though: The best time to exercise is whenever you can, but the best-best time of day to exercise is the time you can stick with for days, weeks and months.

For example, if you’re the person who only has 20 minutes at night, but you keep finding yourself skipping it, ask yourself if there’s a way you can fit it into your morning instead. Perhaps you go to bed 20 minutes earlier and wake up 20 minutes earlier — now you’re still getting in your 20 minutes of exercise; it’s just shifted your schedule a tad. 

The fact of the matter is that people who exercise consistently see better weight loss and fitness results in the long-term. Research also suggests that your body can adapt to regular training schedules, so if you work out every morning, you will probably get a lot better at working out in the morning, and the same in regard to nighttime workouts.

That all said, morning workouts and night workouts both have their advantages and disadvantages as evidenced by decades of scientific research — let’s discuss.

Benefits of working out in the morning

Morning workouts truly do have an edge, according to multiple research studies, and offer a list of benefits that might even sway some night owls to get their fitness on in the morning. 

Can help you establish a fitness routine: People who exercise in the morning are often more consistent simply because morning workouts leave less room for excuses. If you workout first thing in the morning, you can’t skip it in the evening because duties piled up. 

May improve your sleep cycle: Waking up early might be difficult at first, but research suggests that a morning exercise habit can shift your circadian rhythm so that your body is naturally more alert in the morning and more tired in the evening, so you fall asleep earlier and can exercise in the morning again. Morning exercise also seems to boost deep sleep more than evening exercise, according to some research. Plus, sleep helps facilitate muscle growth, so you might even see more strength gains if your circadian rhythm and sleep cycle improve. 

Might burn more fat: Exercising on an empty stomach — in the “fasted state” — is proven to burn more fat than exercising after a meal (in the “fed state”). This happens because your body must utilize fat stores that already exist to fuel exercise, rather than use the food you just ate as fuel. Other research also shows that the “afterburn” lasts longer when you exercise in the morning, which might help you lose weight over time.

Can make you more productive: Research has found that exercising in the morning has a beneficial effect on energy levels, alertness, focus and decision-making, which can translate to a more productive work day.

May boost your mood throughout the day: Morning workouts are a great way to start each day on a high note — the endorphins or “happy chemicals” your body produces in response to exercise can keep your mood elevated long past your hour-long workout. The sense of accomplishment you get after completing a workout can also set you up for an optimistic day.

Downsides to morning workouts

Though a morning exercise habit can be a powerful part of a healthy lifestyle, early morning workouts have their drawbacks, too. When you exercise first thing in the morning, a few things can make your workout a little wonky. 

You might be running on low fuel: If you didn’t eat enough the evening before, you might find yourself battling serious hunger mid-workout. If you wake up hungry most days, try eating a larger dinner or a small, protein-dense snack before bed. You can also eat a small, carb-heavy snack before your morning workout, such as a banana, to help avoid hunger and hunger-related fatigue. 

You may interrupt deep sleep: Depending on your sleep cycle, an early-morning alarm might puncture deep sleep. This can result in sleep inertia (feeling groggy for a while after you wake up), as well as chronic fatigue if it happens often. 

Physical performance isn’t at its peak: Most people don’t roll out of bed feeling nimble and fired up. You might experience stiffness in your joints and temporary inflexibility. You should loosen up as you warm up, but studies actually show that certain strength markers, including peak power, are higher in the evening.

It takes longer to warm up: Speaking of warm-ups, there’s a key reason you might not feel as strong or powerful during morning workouts: Your core body temperature is lower. This makes warming up crucial for morning workouts — jumping into a workout, rather than slowly easing in, can result in injury. This is true all of the time, but especially when your body is cooler.Your heart rate is also slower in the morning (that’s the best time to find your true resting heart rate), which also contributes to needing a longer warm-up.