- In a small study, researchers studied how the bodies of men and women responded to exercising at different times of the day — morning versus night.
- The study followed 30 women and 26 men between 25 and 55 years who were considered “highly active” individuals with an established history of regular exercise — 27 women and 20 men ultimately completed the study.
- The results showed that women burned more fat and improved blood pressure readings by exercising in the morning compared to men who burned more fat at night.
- Several experts not affiliated with the research study noted that sleep and hormone levels can play a significant role in physical performance.
Men and women have different optimum workout times during the day, according to a new study published in Frontiers in Physiology.
Researchers say women burn more fat exercising during morning hours, while men burn more fat at night. Women aiming to improve blood pressure also get better results by exercising in the morning, the study says.
Scientists from Skidmore College in New York, Arizona State University, and California State University, Chico, studied 30 men and 26 women between 25 and 55 years old defined as “highly active” (completing more than 30 mins of structured physical activity 4 days a week for more than 3 years).
Over 12 weeks, researchers analyzed the effects of a varied training program — consisting of stretching, resistance exercise, interval sprints, and endurance training — with the same relative training volume.
Participants did one of the four different exercise routines one day per week for a total of four workouts per week.
One group exercised for an hour between 6:30 a.m. and 8:30 a.m., while the other group followed the same exercise routines, but between 6 p.m. and 8 p.m.
Researchers found that, among women, morning exercise reduced abdominal fat and blood pressure, while evening exercise enhanced muscular performance.
In the male cohort, evening exercise increased fat oxidation and reduced systolic blood pressure and fatigue.
The study concluded that the time of day the subjects exercised “may be important to optimize individual exercise-induced health and performance outcomes in physically active individuals and may be independent of macronutrient intake.”
“Morning exercise in women enhances total and abdominal fat loss, reduces blood pressure, and increases lower body muscle power,” the study said. “Evening exercise greatly increases upper body muscle strength, power, and endurance, and enhances overall mood.”
For men, strength increased after both morning and evening exercise, but evening exercise brought additional benefits with “lower systolic blood pressure and fatigue and stimulates fat oxidation compared to early morning exercise.”
Megan Johnson McCullough is a National Academy of Sports Medicine trainer, professional bodybuilder, and owner of Every BODY’s Fit in Oceanside, CA.
McCullough told Healthline that sleep and hormones both play an important part in optimum workout times.
“Women and men’s sleep patterns are different, which contributes to the difference in results exercise can produce between genders,” McCullough said. “There may be evidence that depending on the time of day and type of exercise performed, cardio versus strength training, there is an optimal choice for women and men to exercise. The differences in sleep cycles correlate to the differences in exercise performance.”
McCullough told Healthline that hormone production and sleep are interrelated. Women spend more time in deep sleep and less time in the lightest sleep phase, compared to men.
“Therefore, it has been suggested that women are more alert and awake in the morning compared to men,” McCullough said. “This notion can relate to women burning more fat when exercising in the morning, partially due to their ability to perform better when the body is more alert during the morning hours. Men might be more alert, and the body is more prepared in the evening time to exercise as a result of needing to wake up the body during the day and then being more alert to exercise later in the day or evening.”
“Research has also shown that cortisol levels are highest in the morning, so there could be a connection to burning more fat in the morning if there’s more stress-induced fat present. Men might take advantage of this and do cardio in the morning to literally ‘burn off’ their stress. This would also lower blood pressure if either gender were to do cardio in the morning,” McCullough told Healthline. “Higher cortisol levels inhibit muscle growth, therefore, strength training at night might be more beneficial. The opposite would be true for women who might lift in the morning when testosterone levels are higher (for them) and there is the strength to lift more weight.”
DJ Mazzoni, a certified strength and conditioning specialist who also serves as the medical reviewer at Illuminate Labs, told Healthline many other factors contribute to the best time for someone to work out.
“What time of day someone performs best at the gym is too individual of a response to provide recommendations by gender,” Mazzoni said. “People of either gender variably prefer working out at different times throughout the day.”
“I’ve found that people perform best at the gym when they go at a time that works best with their schedule, and which they enjoy,” Mazzoni told Healthline. “Some people prefer working out after a long day of work to relieve stress, while others prefer working out at the crack of dawn. Working out when you truly want to work out is likely to lead to improved performance and outcomes compared with working out on a set schedule because you believe it’s a healthier option.
“I do generally recommend avoiding workouts within 3 hours of sleep, because this can disrupt sleep,” Mazzoni said. “People tend to prefer cardio exercises in the morning because they’re not ‘weighted down’ by food. Many people prefer lifting weights after a meal (and post-digestion) because this improves power and performance.”
Jake Dickson is a certified personal trainer and contributing editor at the strength training website BarBend. He said it’s unclear why men and women responded so differently to the timing of exercise.
“However, nighttime exercise is good for men seeking to improve their cardiovascular and metabolic health as well as their emotional well-being. Improving metabolic health reduces the risk of obesity, type 2 diabetes, cardiovascular disease, and stroke,” Dickson explained.
Kent Probst, a personal trainer, movement therapist, and bodybuilder, told Healthline the American College of Sports Medicine’s guidelines for exercise testing and prescription (11th edition, 2022) are the same for men and women.
“There isn’t enough published scientific evidence to make exercise testing and prescription recommendations gender-specific,” Probst told Healthline.
But Probst said time of day indeed matters for anyone working out.
“[With] resistance training, your body temperature peaks between 4 p.m. and 6 p.m., and it’s believed to be the reason pliability, speed, and strength peak during this time frame. Therefore, the optimal time for resistance training is 4 p.m. to 6 p.m. to start maximizing strength and muscle.”
“[For] cardiovascular exercises, muscle stamina and endurance peak around early to mid-morning, meaning this is the best time for cardiovascular exercises,” Probst said. “[For] sports specific exercises, as mental acuity peaks around the middle of the day, sports specific exercises should be done during this time frame.”
