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When Is the Best Time of Day to Work Out?

Here’s what the science says about how to plan exercise to meet your health and fitness goals

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What if you could target the best time of day to work out to burn fat, reduce belly fat, manage diabetes or build muscle? Research suggests there may be better times to work out to help you meet specific fitness goals. You can also time your workouts to help manage certain medical conditions.  

Regular exercise can help you control your weight, lower blood pressure and manage blood sugar and insulin levels. Consistent exercise also helps you build muscle mass and get better sleep. Workout routines can boost your mood and slow cognitive decline.

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So, when is the best time of day to work out? Morning, afternoon and evening exercise each have benefits. But the best time to work out depends mainly on your individual goals.

Here’s what the science says about the best time to work out for specific results.

Morning workouts burn belly fat

“Morning exercise wins the day for optimal belly fat loss,” says Paul Arciero, a doctor of human physiology and nutrition and author of The PRISE Life: Protein Pacing for Optimal Health and Performance. Arciero is the lead author of a 12-week Skidmore College study on morning and evening exercise and a Skidmore College professor.

For the study, healthy, middle-aged men and women worked out with resistance, exercise and rest intervals, stretching and endurance throughout the week. Participants fasted overnight but ate a protein snack before working out in the morning.

Women exercising in the morning lost significantly more belly fat than the women in the evening group. But men in the morning and evening groups didn’t differ in lost belly fat. They lost equally significant amounts of belly fat whether they exercised in the morning or evening.

“It’s likely the men started with greater amounts of belly fat,” Arciero says. “Therefore, they had more belly fat to lose, suggesting that the PRISE fitness routine is equally effective at stimulating belly fat loss in men regardless of the time of day they exercise. Women may have started with slightly less belly fat. Combined with the morning PRISE fitness routine, this triggered a more favorable response with fat burning compared to the evening group.” (Arciero developed the PRISE exercise protocol: protein pacing, resistance training, interval sprint training, stretching and endurance training.)

Better morning results for the women could also be due to differing male and female hormone levels at varying times of day, says Arciero.  “Early morning exercise combined with less available food energy increases fat burning,” he says.

Morning workouts may boost weight loss

The science is mixed on the best time of day to exercise to lose weight. Although a review of multiple studies on exercise and weight loss found that morning exercise at the same time each day may lead to greater weight loss, a study in the research journal Obesity concluded, “there does not appear to be an optimal time to exercise” to lose weight.

“There is no study that definitively talks about a specific time to lose or gain weight,” says cardiologist Nieca Goldberg, M.D., medical director of Atria NYC and clinical associate professor of medicine at the NYU Grossman School of Medicine. No matter what time you work out, combine a healthy diet with exercise to lose weight, she says.

Afternoon workouts can help lower blood pressure

“For high blood pressure and cardiovascular benefit, it's better to exercise in the late afternoon or evening,” Goldberg says.

When you wake up in the morning, you have higher levels of cortisol, epinephrine and norepinephrine, Goldberg says. Those hormones can raise blood pressure. Your arteries are less flexible in the morning, too, which can raise blood pressure, she says. Those factors make exercising in the afternoon ideal if you have high blood pressure.


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Afternoon workouts bring peak performance

If you want to have the most energy and be at your strongest, work out in the afternoon or early evening. Exercise performance changes throughout the day, peaking from 4 p.m. to 8 p.m., according to a review of more than 60 scientific studies on exercise and best times of day for peak performance published in the journal Nature.

The studies varied in methods for defining peak performance times. The review covered studies that measured short, dynamic exercise bouts (for example, less than a minute) and/or exercise over a period of up to three months or longer. Peak performance was defined in some of the studies by electrical activity of muscles and nerves, muscular contraction against resistance and exercise performance.  

A small study also found that performance for strength and endurance exercises peaked in the afternoon from 3 p.m. to 6 p.m.

So, hit the gym, the street or your exercise mat a few hours after eating a protein-packed lunch. That’s the most likely time to achieve peak performance.

Afternoon workouts help manage diabetes

“For people who have type 2 diabetes, studies have shown that afternoon exercise may be better,” Goldberg says. Research also shows that people with type 2 diabetes may have better glucose control if they exercise after a meal, she says.

A four-year study in Diabetes Care found that participants with type 2 diabetes lowered blood sugar levels with afternoon workouts. But if you can’t work out in the afternoon, don’t give up on getting in regular exercise.

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“Some of this data on exercise, timing and diabetes is not set in stone,” Goldberg says. “It’s important for people with diabetes who are engaging in an exercise program to share that with their doctor and have their glucose checked and make sure they’re scheduling regular follow-up visits.”

Low-intensity afternoon and evening workouts can improve sleep

The best time to exercise for better sleep depends on your circadian clock and rhythms. Sleep and wake-up times follow your body’s circadian clock. Circadian rhythms influence when you get sleepy at night. They also play a role in what time you wake up.

The circadian clock resets itself each day, according to the daily cycle of light and dark. But you can reset your circadian clock for better sleep with regular exercise. Still, there’s no one-size-fits-all best time to exercise to reset your circadian clock, according to one study on exercise and circadian rhythm.

The study found that overall, morning exercise caused greater shifts in the circadian clock than evening exercise. But the research also found that your own natural sleep/wake inclination influences, whether you exercise in the morning or evening, are best to reset your circadian clock.

For example, participants who were morning people showed greater shifts in their circadian clock with morning exercise. Yet evening exercise caused delays in resetting their circadian clock. Meanwhile, night owl participants showed advanced shifts with both morning and evening exercise.

Exercise stimulates the circadian clock and allows for better quality sleep because of increased energy spent (burning of calories) and elevated body temperature, says Arciero. “These changes promote an enhanced hormonal environment and eventual lowering of core body temperature that favors better sleep,” he says.

Be careful about adding a heavy strenuous workout late in the day, though. Exercise raises your heart rate and body temperature. That can make it harder to fall asleep.

Lower-intensity endurance or stretching earlier in the afternoon is better for sleep, Arciero says. Avoid intense weight training, resistance training and intervals. Lower-to-moderate-intensity aerobic exercise in the evening can help quiet people down, he says. Mind/body exercises such as yoga are especially good for sleep, he says.

The best time to work out depends on your own best workout time, and also depends on your health, circadian rhythms, hormones and other factors. If you’re exercising to manage diabetes, heart disease and high blood pressure, consult your doctor for the best time to work out. If the hours for “best” workout times aren’t convenient, pick another time. Exercise is beneficial no matter what time of day you do it, Goldberg says.

Is It OK to Work Out on an Empty Stomach?

Working out on an empty stomach may be a “mildly effective” way to lose weight and body fat, says Arciero. But he doesn’t recommend it. That’s because fasting overnight depletes fuel and energy stores of carbohydrates, says Arciero. That leaves mainly your fat stores to be burned.

When energy stores deplete, your body burns both fat and muscle tissue.

“So, while you may be accelerating fat burning during fasted exercise, you are also breaking down and losing more healthy lean body mass (muscle tissue),” says Arciero.

Working out on an empty stomach can also lower how many calories you burn.

“Your body's metabolism compensates by adjusting to a lower level of calorie burning during the exercise and over time may simply recalibrate to a lower metabolism all the time,” says Arciero.

If you’re going to work out on an empty stomach, Arciero recommends the following steps to maximize fat burning while keeping adequate hydration and muscle function. Following these guidelines can also minimize the loss of lean muscle mass and the lowering of your metabolism, he says.

  1. Aim for a maximum of 60 minutes per session at intensity level six or seven (on a scale of 1 to 10).
  2. Work out on an empty stomach no more than one time per week for no more than four weeks at a time.
  3. Make sure to replenish, refuel and rehydrate with electrolytes (sodium, potassium, magnesium, chloride, calcium) during and after, along with 20 to 40 g of high-quality protein within two hours of finishing the workout.

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