This 2-hour window is the best time of day to work out for weight loss, study finds

Day or night, exercise does a body good. But given busy schedules, daily biological rhythms and shifting energy levels, what is the best time to work out?

The debate continues as more research comes in.

"The best time to exercise is when you can fit it in for sure," NBC News medical contributor Dr. Natalie Azar responded. But if you're tackling certain fitness goals, the answer gets more specific.

When it comes to managing obesity and lowering blood sugar, for example, the freshest evidence suggests the timing of physical activity does play a role and gives the edge to evening exercise.

That said, working out at any time can bring many health benefits, including strengthening your muscles and improving heart health.

Working out in the morning is often the easiest option to get fitness into your day, research and experts suggest, especially an unpredictable schedule might get in the way. But people who work out in the afternoon or evening have some advantages too, like being able to fit both cardio and strength training into their routines or coming to their workout already feeling warmed up from the day's other activities.

Here's what to know about timing your workouts to get the most benefits, and the case for each part of the day:

The best time of day to work out

Overall, the experts agree: Exercising in the morning is the best time of day to work out for logistical, effective and health reasons.

When it comes to weight loss, a 2023 study published in the journal Obesity found exercising between 7 a.m. and 9 a.m. could help. Based on data from 5,200 people 20 years old and over, researchers found that moderate to rigorous exercise in the morning was associated with a lower body mass index than exercising midday or in the afternoon.

A few factors could play a role in the findings. For example, morning exercisers were more likely to have never consumed tobacco or alcohol, to consistently work out at the same time every day and to consume fewer calories than midday or afternoon exercisers.

Lead researcher Tongyu Ma, research assistant professor at The Hong Kong Polytechnic University, told NBC News that his "cautious suggestion" from the study is that exercising early in the morning before eating can lead to more weight loss than exercising in other times of day.

But Cameron Mitchell, Ph.D., assistant professor of kinesiology at The University of British Columbia in Vancouver, Canada, who was not involved with the research, told NBC News he could not conclude working out in the morning leads to "optimal health" based on the study results.

It may be that people who exercise in the morning also practice other behaviors that help lower their weight and boost their health.

The benefits of morning exercise

People who naturally wake up earlier in the day manage to squeeze in about 30 minutes more of physical activity a day for men and about 20 minutes more for women, compared to night owls, researchers in Finland found.

Women who exercise between 6 a.m. and 8 a.m. have greater reductions in their belly fat and blood pressure, and they have stronger leg muscles, compared to those who work out in the early evening, researchers reported in 2022 in Frontiers in Physiology.

The exact mechanisms “remain elusive,” the authors wrote, but “morning exercise is increasingly recognized to benefit exercise adherence and weight management in overweight (and) obese individuals.”

Early research shows exercising in the morning could prompt the body's molecular clock, which controls when certain molecules perform certain functions, to reset itself, boosting metabolic health and weight loss, Mitchell said.

Then, there’s the practical side: If you exercise in the morning, you get it over with right away, and there’s less chance of something interfering with your workout — like a last-minute project that forces you to stay late at work — and you have a momentum, Daniel Pink, author of “When: The Scientific Secrets of Perfect Timing,” previously told TODAY.com. Those early sessions can help you lose weight, form a habit or start the day with a mood boost, he added.

People who exercise in the morning feel very good about accomplishing that first thing, Jack Raglin, Ph.D., exercise psychologist and professor at Indiana University School of Public Health-Bloomington, previously told TODAY.com.

“You’ve gotten it out of the way and you’ve got the whole day ahead of you and you can check that off your list,” Raglin noted. Even if it’s tough to pull yourself out bed, you may be pleasantly surprised how good you feel once it’s done.

There’s also the positive impact a morning workout can have on your body. It releases endorphins, which help you feel great.

You may even want to consider exercising before breakfast. People who worked out on an empty stomach after fasting overnight burned double the amount of fat compared to those who exercised after eating the first meal of the day, a 2019 study found.

They were also able to better control their blood-sugar levels and adjusted easily to their before-breakfast workout sessions.

Workouts on an empty stomach are not for everyone, including those with diabetes who are on insulin treatment and could increase their risk of hypoglycemia, Javier Gonzalez, Ph.D., study co-author and a senior lecturer in the department for health at the University of Bath, previously told TODAY.com.

Healthy people who are simply worried they won’t have the energy to get their heart pumping before their morning bagel can try drinking some strong black coffee before their workout to help the exercise feel a little easier, he advised.

The case for afternoon exercise

Exercise during midday and afternoon — defined as the hours between 11 a.m. and 5 p.m. — was linked with a lower risk of premature death from all causes and heart disease compared to working out mostly in the morning or evening, researchers reported in Nature Communications in February 2023.

These benefits were particularly seen among older adults, men, people who were less physically active or those with pre-existing heart disease.

The exact reasons are a mystery, but the authors offered some possible explanations.

It may be due to how the body responds to activity based on its internal clock or circadian rhythm, including faster recovery of systolic blood pressure after exercise in the late afternoon than in the early morning.

Or perhaps eating and light exposure during the day boosted the benefits of afternoon workouts.

Another possibility is that afternoon exercisers engaged in a more comprehensive workout that included both cardio and weights than their morning or evening counterparts, leading to greater health benefits.

The study shows the timing of moderate-to-vigorous intensity physical activity could "maximize the health benefits" of daily exercise, the authors wrote.

The findings were based on data from more than 92,000 people who wore an activity tracker and signed up to be part of the UK Biobank, a database with health information from half a million adults living in the U.K.

The benefits of evening workouts

If you prefer workouts later in the day, they can have their own powerful benefits.

Sedentary people with obesity who do most of their moderate-to-vigorous physical activity in the evening, especially after a meal, have more stable blood sugar levels throughout the day, a 2024 study published in Obesity found.

"The goal here specifically was to lower your blood sugar, having to do with insulin resistance," Azar said.

A separate study, published earlier in 2024 in Diabetes Care, found heart-pumping exercise in the evening — between 6 p.m. and midnight — was associated with the lowest risk of mortality and cardiovascular disease for people with obesity.

The specific reasons are unclear, but research suggests that evening aerobic exercise in particular is associated with improved insulin sensitivity and can significantly reduce blood pressure, the authors wrote.

“Exercise is by no means the only solution to the obesity crisis, but this research does suggest that people who can plan their activity into certain times of the day may best offset some of these health risks," Angelo Sabag, Ph.D., lead author and lecturer in exercise physiology at the University of Sydney, said in a statement.

Evening exercise — between 6:30 p.m. and 8:30 p.m. — also “greatly” increases upper body muscle strength, power and endurance, and enhanced overall mood for women, according to the study published in Frontiers in Physiology. For men, the p.m. workouts lowered systolic blood pressure and fatigue, and stimulated fat oxidation compared to early morning exercise.

If you want to enjoy your workout more and find it less of a struggle, the late afternoon or early evening may be better. You’re warmed up, leading to a better performance.

“I tend to feel pretty creaky in the morning, but later in the day, I don’t feel creaky at all,” Pink said.

Plus, you can get the stresses of the working hours out and make the exercise session a ritual to end your day beneficially, Raglin noted.

This article was originally published on TODAY.com