Women who exercise in the morning lose more belly fat and have lower blood pressure, study suggests

• Women who exercise in the morning lose more belly fat than evening exercisers, a study suggests.
• For men, evening exercise lowers blood pressure and reduces belly fat more than morning exercise.

Morning exercise may be best for belly fat loss in women, and evening workouts better for increasing upper body strength, according to a new study.

The research, carried out on 47 adults by Skidmore College, New York, also found 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.

One group exercised for an hour between 6 a.m. and 8 a.m., and the others worked out between 6.30 p.m. and 8.30 p.m. They were assessed for various metrics at the start and finish, including bench and leg press, body composition, and blood pressure, and food intake was also analyzed.

"For women, exercise during the morning reduces belly fat and blood pressure, whereas evening exercise increases upper body muscular strength, power, and endurance, and improves overall mood and nutritional satiety," lead study author Paul Arciero told Insider.

While all 27 women in the 12-week trial reduced their total body fat, stomach and hip fat, and blood pressure, these improvements were greater in morning exercisers.

Morning exercise can lead to healthier food choices

A calorie deficit is required for fat loss, and training in the morning could lead people to consume fewer calories over the course of the day, previous research suggests.

This could have played a role in the study's results, but there were no differences between the nutritional intake data of the AM and PM groups' diets, Arciero said, so he doesn't think it would be a major factor.

Personal trainer Ben Carpenter, however, said the research should be interpreted with nuance.

This is not the first time researchers have assessed morning vs evening exercise and found that timing can make a difference — existing research suggests evening training benefits strength improvements, and also that morning exercise is linked to better weight loss — but there's not enough data to form a firm conclusion, he said.

"The theories essentially hinge on hormonal changes and circadian rhythms. Bodily processes are not uniform throughout every single hour of the day, some hormones go up and down," Carpenter told Insider.

Carpenter points out that the study didn't assess what time of day the participants were normally working out before, and what you're used to makes a difference as the body takes time to adjust to new routines.

The best exercise time is what you'll stick to, Carpenter said

Arciero says the research is significant enough that people should alter their training time depending on their goal, but Carpenter isn't convinced.

The diverging data in the study could be confusing, say, for a woman wanting to lose fat and get stronger, he said.

For people who are not professional athletes, fitting exercise into their lives is challenging enough that they don't have the luxury of considering when might be "optimal," Carpenter said.

We should encourage people to be active whenever works best for them and will be sustainable, he said.

"If you work harder in the evening because you like going to an exercise class with your friend vs training alone in the morning, that could be an additional stimulus for results," he said.

Finding a form of exercise you enjoy and will stick with until it becomes a habit matters most, he said.

"Engaging in a good exercise programme consistently is always going to beat engaging in an optimal exercise programme sporadically," Carpenter said.

Once that habit is ingrained, then you can start trying different timings.

"If you are just getting started, don't spend too much time worrying about the minor details," Carpenter said.