WIf you have a busy schedule, try to exercise whenever you can. But there’s growing evidence that when you exercise can make a difference to its effects. Our latest research shows that body fat responds differently to exercise depending on the time of day At least in mice.
Our latest study found that when rats performed a single exercise session in the late morning (about three hours after waking), they burned more adipose tissue (body fat) than rats who exercised in the late evening. Simultaneously, we observed a change in the way adipose tissue genes responded after exercise.
morning exercise is more effective
Using mice to gather evidence about what happens in our own physiology is common because humans have one in almost every set of genes. closely related forms in rats. This raises the possibility that the effect we see in mice may be similar to what we would expect to see in humans.
To conduct our study, we engaged rats in an intense exercise session during their active phase (equivalent to our late morning) or resting phase (equivalent to our late evening). We took adipose tissue samples every four hours after exercise for a total of 20 hours after exercise to understand the effect of different timing.
Fatty acids are released into the blood by adipose tissue, which provide the body with energy to use During exercise, while reducing the size of fat cells.
Rats who exercised late in the morning showed increased fatty acid levels in their blood immediately after exercise and 12 hours after exercise. But the late evening exercisers showed no such change. This indicates that the late-morning exercisers experienced twice as much fat loss.
Even more interestingly, the unique timing benefits of exercise were also seen in the way genes worked. The genes that late morning exercise increased were related to fat burning (breakdown), heat production (energy utilization) and blood vessel production. All of these changes are beneficial for body fat loss and blood sugar regulation, which can benefit body weight and health.
This research agrees with two previous studies, which have shown that exercise timing matters for many tissues – such as muscle and liver, Recent work in humans has also suggested how training at different times of the day may affect the body. reacts to insulinA hormone important for controlling blood sugar and therefore body weight.
body clock
The biological circadian clock may be a major reason for the way the body responds to exercise depending on the time of day.
Every cell in the body has a circadian clock that coordinates metabolism with changes in light, nutrition, and movement throughout the day. hormones, body temperature Even more sensitivity to sounds All are affected by the body clock.
Body fat is no different: It has its own clock, which regulates the expression of many genes. based on our findings and Findings from other studiesWe hypothesize that the timing of exercise may interact with the circadian clock to program fat cells to burn fat better.
also regulates circadian rhythm when food is eaten By making us hungry in broad daylight. This is so that our body gets the required energy throughout the day to perform all its functions.
So when we exercise, the body taps into the foods we’ve recently eaten for energy. However, if there is no food, it has to primarily use fatty acids derived from adipose tissue for energy.
For this reason, we were interested to know whether the benefits of exercising late in the morning are similar to those of exercising on an empty stomach. We had rats in the late evening group exercise under fasted conditions to see if we could make them respond to exercise as well as morning rats.
We found that fasted evening exercise increased signs of body fat breakdown in the blood. However, there were no signs of any gene changes. This surprising finding suggests that the circadian clock may fine-tune how the body responds to exercise — overriding the effects of meal timing.
When should I exercise?
Our study was conducted only on rats and for only one exercise session, so it is difficult to generalize to the best exercise time for people. More research will be needed to determine how exercise timing affects fat burning in humans, and if our findings are consistent across multiple exercise sessions. This is the next step in our research at the Karolinska Institute.
In the meantime, the best general advice right now is to stay active and engage in exercise – even when you are able to work out. exercise is still a great way to lose excess body fatwhich may help reduce your risk of certain diseases such as heart disease And diabetes type 2, But if you’re able to taper off your early morning workouts, it could potentially help you burn more fat.
PhD Researcher in Integrative Physiology, Karolinska Institutet
Chair Professor of Clinical Integrative Physiology, Karolinska Institutet
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