When should you exercise? Time of day leads to different workout results

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SARATOGA SPRINGS, N.Y. — The time people exercise probably comes down to when they can fit it in to their busy schedules more than anything else. However, a new study finds the best time to work out may depend on what kind of health benefits you’re looking to achieve.

Researchers have found that “Exercise Time Of Day” (ETOD) leads to different workout results for both men and women. Specifically, women who work out in the morning are more likely to lose excess belly fat, while men who work out at night burn more fat.

The study is the first randomized controlled trial to show that changing the time you work out, as well as engaging in different types of exercise, leads to different results depending on gender.

“Here we show for the first time that for women, exercise during the morning reduces belly fat and blood pressure, whereas evening exercise in women increases upper body muscular strength, power, and endurance, and improves overall mood and nutritional satiety,” says principal investigator Dr. Paul Arciero, a professor at the Health and Human Physiological Sciences Department of Skidmore College, in a media release.

“We also show that for men, evening exercise lowers blood pressure, the risk of heart disease, and feelings of fatigue, and burns more fat, compared to morning exercise.”

RISE workout program leads to big benefits

Study authors recruited 30 women and 26 men for their experiment. All of the participants were between 25 and 55 years-old, generally healthy, active, non-smokers, with a normal weight. Over 12 weeks, they trained with exercise coaches using the RISE program — which focuses on resistance (R) training, sprint interval (I) training, stretching (S) training, or endurance (E) training for 60 minutes depending on the day of the week.

The group also followed a special diet, keeping protein intake between 1.1 and 1.8 grams per kilogram of body weight each day. Participants trained four days a week, but researchers also split the group into two different workout sessions.

Half of the participants exercised between 6:30 and 8:30 a.m. each morning while the other half exercised between 6 and 8 p.m. at night. Additionally, those working out in the morning did not eat before their session and then had four meals at four-hour intervals afterwards. The night group ate three meals throughout the day and then had one last meal after their workout.

Researchers examined several measures of physical health, including the group’s aerobic power, muscular endurance, flexibility, balance, upper and lower body strength, and jumping ability. They also measured each person’s blood pressure and biomarkers of heart health — including arterial stiffness, total and “good” HDL cholesterol, and percentage of fat.

Overall, the study finds the unique mix of exercises improves all measures of health, regardless of when people exercise.

“Our study clearly demonstrates the benefits of both morning and evening multimodal (RISE) exercise to improve cardiometabolic and mood health, as well as physical performance outcomes in women and men,” Arciero reports.

Timing is everything

Despite the not-so-surprising finding that exercise at any time of day improves health, there were key differences in the morning and night groups.

Specifically, all female participants reduced their total body fat and blood pressure during the 12 weeks, but women working out in the morning were saw greater reductions in abdominal and hip fat.

Meanwhile, men in the trial were more likely to see improvements in their cholesterol, blood pressure, respiratory exchange ratio, and carbohydrate oxidation by exercising at night.

“Based on our findings, women interested in reducing belly fat and blood pressure, while at the same time increase leg muscle power should consider exercising in the morning. However, women interested in gaining upper body muscle strength, power and endurance, as well as improving overall mood state and food intake, evening exercise is the preferred choice,” Arciero says. “Conversely, evening exercise is ideal for men interested in improving heart and metabolic health, as well as emotional wellbeing.”

“We have shown that ETOD should be an important consideration for anyone, women and men, given its effects on the strength of physiological outcomes of exercise. But regardless of ETOD, regular exercise is essential for our health,” adds second author Stephen Ives, an associate professor at Skidmore College.

The study is published in the journal Frontiers in Physiology.

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