Physical activity done in the evening provides the most benefit for sedentary adults who are overweight or obese, according to a new study published in Obesity.
Moderate-to-vigorous physical activity in the evenings was associated with the greatest reductions in blood sugar. The results were particularly significant in those with metabolic impairments who have difficulty regulating their blood sugar levels.
“Our results highlight the importance of the field of precision exercise prescription,” Jonatan Ruiz, a professor of physical activity and health at the University of Granada in Spain and one of two corresponding authors of the study, said in a statement. “In clinical practice, certified sports and medical personnel should consider the optimal timing of the day to enhance the effectiveness of the exercise and physical activity programs they prescribe.”
Timing of Exercises
Research has established that exercise helps the body regulate blood sugar levels, especially in people struggling with weight or metabolic diseases.Mr. Ruiz and his team found that both men and women who completed more than half of their exercise in the evening had lower daytime, nighttime, and overall blood glucose levels.
To determine the effects of timing on exercise benefits, the researchers recruited 186 individuals to participate in the study. Half of the participants were women, and the average age of participants was about 46 years old. All were overweight or obese, with an average body mass index (BMI) of 32.9 kilograms per square meter (32.9 kg/m2). According to the Centers for Disease Control and Prevention (CDC), a person with a BMI between 25 and 29.9 is considered overweight, while individuals with a BMI higher than 30 are considered obese.
While the research team didn’t impose an exercise routine on the participants, they measured any physical activity that participants engaged in, classifying it by the time of day completed.
All exercises helped participants lower their glucose levels. The group reduced its 24-hour average glucose by one milligram per deciliter (mg/dL) during somewhat active days and up to 1.5 mg/dL on very active days. However, the researchers found that average glucose levels were lower when most of the moderate-to-vigorous exercise was done during the evening, amounting to a 2.16 mg/dL reduction.
“This association was stronger in those participants with impaired glucose regulation. The pattern of these associations was similar in both men and women,” the authors wrote.
The authors said it is still unclear why the drop in blood sugar levels differed based on the time of the physical activity but suggested that the body’s circadian rhythms could be a reason.
The skeletal muscles, which are responsible for physical movement and help reduce blood sugar levels by burning sugar, become less capable of breaking down sugar in the evening. Insulin is a signal that the body sends to the muscles to take in and break down sugar, but skeletal muscles become less sensitive to insulin at this time of day.
“Consistent evidence has revealed the existence of a diurnal rhythm in glucose tolerance and insulin sensitivity because these functions are relatively impaired in the evening compared with the morning,” the authors wrote, noting that people with type 2 diabetes may be at risk of spiking their blood sugar levels if they exercise in the morning.
“As the field moves towards individualized exercise prescriptions for different chronic conditions, this study now provides additional insights beyond just telling patients to ‘move more,’ but instead to move as often as possible and to prioritize afternoon-to-evening movement when feasible for glucose regulation,” Renee Rogers, a senior scientist at the University of Kansas Medical Center who was not involved in the study, said in the statement.
Get Moving to Prevent Obesity and Diabetes
The CDC recommends that all American adults exercise moderately to vigorously for at least 150 minutes per week, with two days of muscle-strengthening activity. However, the agency never specified the best time for people to exercise.Excess weight can lead to obesity, a significant contributor to diabetes. From 30 percent to 53 percent of new type 2 diabetes cases are linked to obesity, which elevates a person’s risks of cardiovascular disease and stroke. However, type 2 diabetes can be prevented or delayed with lifestyle changes such as losing weight, exercising, and eating healthily.
According to the National Diabetes Prevention Program, changes in behavior can help people with prediabetes to lose 5 percent to 7 percent of their body weight, reducing the risk of type 2 diabetes by 58 percent.
