Exercising at different times of the day may have varying impacts on men and women, according to a new study.

The study found that women who exercised in the morning had reduced abdominal body fat and blood pressure compared to those who exercised in the evening. However, women who trained later in the day had enhanced muscular performance compared to the other group.

The men in involved in the trial were less effected by time of day, but evening exercise increased fat oxidation and reduced systolic blood pressure and fatigue.

All participants did the same exercises and followed a meal plan

In total, 30 women and 26 men were included in the study. Participants were non-smoking, healthy, trained women and men with no known cardiovascular or metabolic diseases.

All participants were highly active, lean, middle aged (25–55 years), and weight stable for at least six months prior to the beginning of the study.

The participants were matched for body weight, BMI and percent body fat and then randomly assigned to one of two groups.

One group performed resistance, interval, stretching, endurance (RISE) training for an hour between 6:00 and 8:00am while the other group did the same activities for one hour between 18:30 and 20:30.

Both groups were also provided with a healthy meal plan and support from a dietitian, with a weekly meeting for the first two weeks and thereafter as needed.

All physical performance outcomes improved in the men and women from both groups

The results showed that all physical performance outcomes improved in the men and women from both groups, including upper and lower body muscle function.

While total body fat mass and body fat, abdominal and hip fat decreased in both AM and PM groups for men and women, the magnitude of improvement was significantly greater in AM exercisers for total body fat mass and abdominal fat percentage in women.

Additionally, women in both AM and PM exercise groups had significantly decreased total cholesterol, systolic and diastolic blood pressure, aortic and brachial augmentation index, whereas in the men’s group, all cardiometabolic variables were unchanged in AM exercisers.

In the PM group however, men’s total cholesterol:HDL-cholesterol, systolic blood pressure (SBP) and respiratory exchange ratio (RER) declined significantly. Most notable was the significant reduction in RER in PM versus AM men exercisers, which mirrored a significant increase in fat oxidation and decrease in carbohydrate oxidation.

More research is needed to find out why these results occurred

The authors of the study say the study highlights that women and men respond differently to exercise time of day (ETOD) and therefore, “careful attention should be used in matching physical performance, cardiometabolic, and psychological mood state goals with the scheduling of multi-modal exercise training to optimize results”.

For women interested in losing abdominal weight and improving their blood pressure, morning exercise could lead to the quickest results. However, evening exercise may be best for those looking to improve their muscle strength and overall mood and food intake.

The men involved in the trial were less sensitive to the time of day they exercised, but evening exercise appears to be best for improving heart and metabolic health.

The researchers add that it is not clear exactly why men and women's responses to the timing of exercise were so different, and more research is needed to find out more. They note, however, that all exercise is beneficial and the best time to do it is whenever you can fit it into your schedule.