If you could give your body an edge, burn more calories, and get more health benefits simply by hitting the gym at the perfect time, you probably would, right? Unfortunately, that perfect time isn’t so clear-cut; research tells us there are benefits to working out at various times throughout the day.
A 2012 BYU study published in the journal Medicine & Science in Sports & Exercise, for instance, measured how women responded to food after exercising first thing in the morning. When the 17 participants with healthy weights and BMIs and 18 obese participants walked briskly for 45 minutes, they were less distracted by crave-inducing food photos than when they completed no exercise at all. On top of that, they also upped their physical activity more throughout the day after walking in the morning, regardless of body weight. And the benefits don't stop there. We also know morning exercise revs metabolism, so if you hit the gym in the AM, you'll be burning through the calories during the day while you're taking them in instead at night while you're asleep.
Lara Carlson, Ph.D., associate professor of applied exercise science at University of New England and President-elect of the New England chapter of the American College of Sports Medicine, says that if you're looking to shed weight or improve overall health, studies are starting to favor the morning. "For weight loss, it's more controversial, but there's research that has looked at people engaging in morning versus afternoon exercise, and those who exercise in the morning have lower blood pressure throughout the day and get better sleep," she says. “Sleep is when your body repairs itself, and sleep also reduces stress, which may affect your weight—and I think future research will begin to tie the benefits of morning exercise together better.”
On the flipside, though, working out later in the day also has proven benefits. A 2010 study published in the journal Chronobiology International analyzed the role of the body's internal clock on athletic performance. The researchers determined that as body and environmental temperature increase in late afternoon, so does enzyme activity and muscular function, so you can work out at your peak from about 2 p.m. to 6 p.m. Working out after work can also be beneficial. You'll likely have more energy than if you try to drag yourself out of bed in the morning. And sinceresearch tells us you only need a 20-minute endorphin burst to unwind, fitting in a quick workout can help you relax after a rough day at the office.
If she had to choose, Carlson would say to work out in the morning. "I tell people if you make it the first thing you do, research shows you're more likely to adhere," she says.
But with that in mind, know this: You definitely don't have to exercise in the a.m. if it's just not your cup of tea. "I've worked with some people who simply cannot get up for a morning workout—and that's fine," says Carlson. So don't stress if you're not a morning person. The most important thing is that you fit in some sweat time at all.