- A new study published this week found working out in the afternoon and evening may help control blood sugar.
- Researchers found that time spent doing moderate to vigorous physical activity reduced both liver fat content and insulin resistance.
- The team found no significant difference in insulin resistance in people who were more physically active in the morning or throughout the day.
New research finds exercising in the afternoon or evening could better help control blood sugar than other physical activity performed throughout the day.
The study, published November 1 in the journal Diabetologia concluded that exercising between noon and midnight could significantly decrease insulin resistance compared to activity earlier in the day.
“Our aim was to investigate associations of timing of physical activity and breaks in sedentary time with liver fat content and insulin resistance in a middle-aged population,” lead study author, Jeroen van der Velde, PhD, Department Clinical Epidemiology at Leiden University Medical Center, told Healthline.
The team analyzed data from the Netherlands Epidemiology of Obesity (NEO) study, which included men and women aged 45 and 65 years who had a body mass index (BMI) of 27 or greater, meaning they were overweight or obese.
They then invited all inhabitants between 45 and 65 years old with a BMI representative of the general population from one municipality in the Netherlands as a control group, for a study population of nearly 6,700 people.
All participants underwent a physical exam where blood samples were taken to measure blood glucose and insulin levels when they were fasting and after eating.
They were also questioned about their lifestyles and some were chosen to have their liver fat content measured by MRI scan.
A random sample of 955 participants were given a combined accelerometer and heart rate monitor to use 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 PM to 6 PM, and 6 PM to midnight, 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 physical activity energy expenditure, which allowed researchers to determine the amount of time spent at various activity intensities.
Only 775 people with complete data were included in the analysis.
The researchers found that compared to spreading activity throughout the day, exercising in the afternoon was linked to an 18 percent reduction in insulin resistance and doing so in the evening with a 25% reduction.
They also found that time spent doing moderate to vigorous physical activity reduced both liver fat content and insulin resistance.
However, van der Velde and team found no significant difference in insulin resistance between morning activity and exercise spread evenly over the day.
van der Velde said he wasn’t surprised that afternoon or evening physical activity appears most beneficial, because previous studies performed in patients with diabetes showed most beneficial effects on glucose control were when high-intensity exercise was performed in the afternoon rather than in the morning.
“However, in our study we examined habitual moderate-to-vigorous physical activity,” he said. “Habitual MVPA does include high-intensity exercise, but is mostly comprised of brisk walking and cycling – the latter especially in the Netherlands.”
He noted that he and his team still observed differences of up to 25 percent in insulin resistance between those mostly active in the evening versus the group with evenly distribution MVPA throughout the day.
“This big of a difference was not expected,” said van der Velde.
Dr. Ricardo Correa, director of the Endocrinology, Diabetes and Metabolism Fellowship Program in the University of Arizona College of Medicine explained that insulin resistance occurs when cells stop responding to insulin.
“So what the receptor of insulin does is that whenever insulin comes, [it] activates a cascade so glucose can enter the cell,” he said.
“What happens when that receptor is damaged is that it can’t activate the cascade so glucose cannot come in,” he continued. “And [this] will cause all the glucose to stay outside the cell.”
If glucose can’t get into the cells, blood sugar remains high resulting in type 2 diabetes.
Correa cautioned that people who are overweight or obese are at greatest risk for insulin resistance.
“Insulin resistance is the first step of the progression to type 2 diabetes,” he said.
“We are just starting to comprehend to potential health benefits of timing of physical activity,” said van der Velde.
He emphasized that for this study, he looked at differences in insulin resistance on a group level.
“So, in order to translate our findings into individual advice, there are several things we need to understand,” he continued.
He said one thing is whether adapting daily activity from the morning to the afternoon or evening will indeed lead to improvements in insulin sensitivity.
“Also, we do not know if everyone will benefit from changing their timing of activities,” said van der Velde.
“Maybe, people that can be characterized as a morning person actually will benefit more from physical activity earlier in the day,” he added. “For now, I think we should await future studies to translate our findings into clinical messages.”
Correa explained that physical activity offers another pathway that does not involve insulin signaling. “So the two ways that glucose can enter 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 whenever we do exercise, we allow entry of glucose into the cells because glucose provides energy in exercise, so that’s a way the body has to get energy,’ he explained.
According to Correa, it’s a “little bit controversial” to say one time is better than another for exercise, “because exercise anytime of day is beneficial.”
He pointed out that the study used a relatively small group to discover their findings.
“I think we have to look at it with a grain of salt,” he cautioned. “Because if we recommend to a patient to do exercise it would depend on when they are available to do it. Some of them are available in the morning – so we should not 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 obese or overweight people.
Experts say that this doesn’t mean we should only exercise later in the day, because exercise is beneficial at any time.
They also say that they still don’t know whether everyone will see the same benefits from evening exercise and more research is needed to find out.