Exercising at night is more efficient for metabolism, says study

Evening exercise may be more powerful than morning workouts for improving metabolic health, according to a study on exercise timing.

The study, which looked at high-fat diets and overweight men, found that exercise later in the day moderated the undesirable health effects of a fatty diet, while morning exercise did not.

The participants were only men who were on a high-fat diet, but the evidence adds that timing of exercise is important and, for many people, working out later can have particular advantages.

Although we may only be vaguely aware of it, the operations inside our bodies follow busy, intricate, and changing circadian schedules.

All of our tissues contain molecular clocks that coordinate biological systems, causing blood sugar to rise and fall throughout the day, along with hunger, heart rate, body temperature, sleepiness, gene expression, muscle strength, cell division, energy expenditure. energy and other processes.

The full workings of these internal clocks remain mysterious. But scientists know that they recalibrate themselves based on complex signals from inside and outside our bodies. This means that they are synchronized with light and sleep. They are also defined by meals, which means that when we eat, as well as what we eat, can influence our health and metabolism.

Most researchers believe that the timing of exercise also sets internal clocks. But the results of relevant previous studies have been inconsistent. Some suggest that morning exercise before breakfast burns more fat than night exercise. Others think otherwise.

And some recent experiments indicate that exercising earlier, if intense, actually impairs blood sugar control, while the same exercise, performed later, smooths blood sugar spikes and improves metabolic health, which can benefit. particularly heart health and the management of type 2 diabetes.

Most of these studies, however, focused on one type of exercise and rarely controlled people’s meals during the experiments, making it difficult to separate the effects of exercise timing from what people eat and when.

For this study, published last year in the journal Diabetologia, scientists affiliated with the Mary MacKillop Health Research Institute at the Australian Catholic University in Fitzroy, Australia, and other institutions, decided to control people’s diets while adjusting their training schedule.

They started by recruiting 24 overweight and sedentary Australian men (women were not included to avoid menstrual cycle issues). Scientists invited these volunteers into the lab, checked their aerobic fitness, cholesterol, blood sugar control and other health aspects, asked about their current eating habits, and then prepared them with meals.

The meals consisted of about 65% fat, as the researchers wanted to know how the timing of exercise would affect fat metabolism as well as blood sugar control.

The volunteers ate the unctuous foods for five days and visited the laboratory for further testing. Then the scientists divided them into three groups. One would start exercising every day at 6:30 am, another at 6:30 pm, and the last would remain sedentary as a control.

The exercise routines were identical, mixing short, intense intervals on stationary bikes one day with easier, longer workouts the next. The practitioners exercised for five consecutive days while on the high-fat diet. Then the researchers repeated the original tests.

The results were disturbing, in a way. After the first five days of the fatty diet, the men’s cholesterol had risen, especially LDL, the less healthy type. Their blood also contained altered levels of certain molecules related to metabolic and cardiovascular problems, with changes that suggested increased risk of heart disease.

Morning exercise, however, did little to mitigate these effects. The morning exercisers showed the same high cholesterol and worrisome molecular patterns in their blood as the control group.

Nighttime exercise, on the other hand, lessened the worst impacts of poor diet. The late exercisers showed lower cholesterol levels after the five workouts, as well as better patterns of cardiovascular health-related molecules in the bloodstream.

Surprisingly, they also developed better blood sugar control overnight after workouts, while sleeping, than any of the other groups.

The upshot of these findings is that “nighttime exercise reversed or reduced some of the changes” that accompanied the high-fat diet, says Trine Moholdt, an exercise scientist at the Norwegian University of Science and Technology, who led the study in Australia as a visiting researcher. “Morning exercise didn’t do that.”

That study doesn’t tell us how or why late exercise was more effective at improving metabolic health, but Moholdt suspects it has a greater impact on molecular clocks and gene expression than morning workouts.

She and her colleagues intend to investigate these questions in future studies and also look at the effects of exercise timing among women and older adults, as well as the interaction between exercise timing and sleep.

For now, she cautions that the study in no way suggests that morning workouts aren’t good for us.

Men who exercised became more aerobic, she says, regardless of when they exercised. “I know people know this,” she says, “but any exercise is better than no exercise.”

Working out later in the day, however, can have unique benefits for improving fat metabolism and blood sugar control, particularly if you eat a high-fat diet.

Translated by Luiz Roberto M. Gonçalves