Type 2 Diabetes: Exercising Later Cuts Blood Sugar, Insulin Resistance

The team analyzed data from the Netherlands Epidemiology of obesity (NEO), which included men and women ages 45 and 65 who had a body mass index (BMI) of 27 or higher, meaning they were overweight or obese.

They then invited all inhabitants between 45 and 65 years of age with a BMI representative of the general population of a municipality in the Netherlands as a control group, for a study population of almost 6,700 people.

All participants underwent a physical exam where blood samples were taken to measure blood glucose and insulin levels when fasting and after eating.

They were also asked about their lifestyles and some were chosen to have their liver fat content measured using MRI.

A random sample of 955 participants was given a combined accelerometer and heart rate monitor to wear for four consecutive days and nights to monitor their movements and activity.

The day was divided into three blocks; 6 AM to 12 PM; 12:00 to 18:00 and 18:00 to 00:00, with the proportion of total daily moderate to vigorous physical activity (MVPA) occurring in each revealing the most active period.

These measurements were used to estimate the energy expenditure of physical activity, which allowed the researchers to determine the amount of time spent at various intensities of activity.

Only 775 people with complete data were included in the analysis.

The researchers found that, compared to the distribution of activity throughout the day, exercising in the afternoon was associated with an 18% reduction in insulin resistance and exercising in the evening with a 25% reduction.

They also found that time spent in moderate to vigorous physical activity reduced both liver fat content and insulin resistance.

However, van der Velde and his team found no significant difference in insulin resistance between morning activity and exercise spread evenly throughout the day.

van der Velde said he was not surprised that physical activity in the afternoon or evening seemed to be more beneficial, because previous studies in patients with diabetes showed that the most beneficial effects on glucose control were when exercise high intensity was done in the afternoon instead of in the morning.

“However, in our study we looked at regular moderate to vigorous physical activity,” he said. “The usual MVPA includes high-intensity exercise, but it is mainly made up of brisk walking and cycling, the latter especially in the Netherlands.”

He noted that he and his team still saw differences of up to 25 percent in insulin resistance between those who were more active at night and the group with an even distribution of MVPA throughout the day.

“This big difference was not expected,” van der Velde said.

dr richard strapdirector of the Endocrinology, Diabetes and Metabolism Fellowship Program at the University of Arizona School of Medicine, explained that insulin resistance occurs when cells stop responding to insulin.

“So what the insulin receptor does is that every time the insulin arrives, [it] it activates a cascade so that glucose can enter the cell,” he said.

“What happens when that receptor is damaged is that it can’t activate the cascade, so glucose can’t get in,” he continued. “Y [this] it will cause all the glucose to stay out of the cell.”

If glucose cannot enter the cells, the blood sugar level remains high and type 2 diabetes occurs.

Correa warned that people who are overweight or obese are at greater risk of insulin resistance.

“Insulin resistance is the first step in the progression to type 2 diabetes,” he said.

“We are beginning to understand the potential health benefits of the timing of physical activity,” van der Velde said.

He emphasized that for this study, he looked at differences in insulin resistance at the group level.

“So in order to translate our findings into individual advice, there are a number of things we need to understand,” he continued.

He said it’s one thing whether adapting daily activity from morning to afternoon or evening will lead to improvements in insulin sensitivity.

“Also, we don’t know if everyone will benefit from changing the schedule of their activities,” van der Velde said.

“Perhaps people who can be characterized as early risers will actually benefit more from physical activity earlier in the day,” he added. “For now, I think we should wait for future studies to translate our findings into clinical messages.”

Correa explained that physical activity offers another pathway that doesn’t involve insulin signaling. “So the two ways glucose can get into the cell,” he said, “are through the insulin receptor or through exercise.” Therefore, exercise can help with blood sugar control, which in turn can help improve insulin sensitivity.

“So every time we exercise, we allow glucose into the cells because glucose provides energy during exercise, so it’s a way for the body to get energy,” he explained.

According to Correa, it is “a bit controversial” to say that one hour is better than another to exercise, “because exercising at any time of the day is beneficial.”

He noted that the study used a relatively small group to discover its findings.

“I think we have to look at it with a grain of salt,” he warned. “Because whether we recommend a patient to exercise would depend on when they are available to do it. Some of them are available in the morning, so we shouldn’t recommend that patients only exercise in the afternoon.”

New research found a link between exercising later in the day and a reduction in insulin resistance in overweight or obese people.

Experts say this doesn’t mean we should only exercise later in the day, because exercise is beneficial at any time.

They also say they don’t yet know if everyone will see the same benefits from nighttime exercise, and more research is needed to find out.