The idea that exercise benefits metabolic health is widely accepted. But whether the benefits of exercise are greater depending on when one exercises – morning versus afternoon – is a matter of considerable debate. A recent study shows that morning exercise reduces blood pressure, fasting insulin, and insulin resistance better than afternoon exercise in people with metabolic syndrome.

Metabolic syndrome is a constellation of conditions characterized by abdominal (central) obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides, and low high-density lipoproteins. Having metabolic syndrome increases a person’s risk of cardiovascular disease and type 2 diabetes. Roughly one-third of adults between the ages of 20 and 60 have metabolic syndrome.

The study involved 139 adults with metabolic syndrome who agreed to participate in three supervised high-intensity interval training sessions every week for 16 weeks. About a third of the participants performed their exercise in the morning, a third did so in the afternoon, and a third didn’t engage in any exercise. Researchers measured the participants' body composition, cardiorespiratory fitness, maximal fat oxidation, blood pressure, and blood metabolites before and after the intervention.

They found that both exercise groups demonstrated greater body fat loss, reduced waist circumference (nearly an inch), and lower diastolic blood pressure than those who didn’t exercise. However, when comparing the morning exercise group to the afternoon group, they found that morning exercise was more effective at reducing systolic blood pressure (4 percent drop vs. 1 percent), lowering fasting insulin (12 percent drop vs. 5 percent), and decreasing insulin resistance (14 percent drop vs. 4 percent).

These findings suggest that morning exercise boosts cardiometabolic health better than afternoon exercise. The investigators posited that these effects may be related to circadian rhythms, which influence the body’s response to exercise and dietary intake.

Finding the time or motivation to exercise in the morning may be challenging for many. Fortunately, most experts agree that some exercise is better than none, as long as it’s not too close to bedtime. Learn more in this clip featuring Dr. Rhonda Patrick.