Best time of day to exercise if weight loss is your goal
While, of course, exercise has great benefits whenever you choose to do it, can the time of day you work out affect your goals differently?
The answer seems to be yes. For example, morning exercise may be the best way of burning fat, a new study suggests.
Physical activity at the right time of day appears to help with increasing fat metabolism, according to the Swedish study, which looked at mice.
It unearthed that mice who exercised in an 'early active phase' – representing morning exercise in humans – increased their metabolism more than mice who did physical activity at a time when they usually rest.
"Our results suggest that late-morning exercise could be more effective than late-evening exercise in terms of boosting the metabolism and the burning of fat, and if this is the case, they could prove of value to people who are overweight," said Professor Juleen Zierath, from the department of molecular medicine and surgery and the department of physiology and pharmacology, Karolinska Institutet, Sweden.
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Researchers also say that physical activity at different times of day can affect the body in different ways as biological processes depend on the *circadian rhythms of the cells (*the 24-hour sleep-wake cycle that's part of the body's internal clock).
To explore how this affects the burning of fat, scientists at the Karolinska Institutet and the University of Copenhagen studied the body fat of mice after a session of high-intensity exercise on a treadmill, performed at two points of the daily cycle.
They looked at both an 'early active phase' – as mentioned above – and an 'early rest phase' – representing a late evening session in humans.
After studying fat metabolism and analysing which genes were active in fat tissue after exercise, they found morning exercise was better. Physical activity at an early active phase increased the expression of genes involved in the breakdown of fat (adipose) tissue, thermogenesis (heat production) and cells in the adipose tissue that indicate a higher metabolic rate (and this is thought to help with burning more calories).
These effects were seen only in the mice that exercised in the early active phase and were independent of food intake.
"The right timing seems to be important to the body’s energy balance and to improving the health benefits of exercise, but more studies are needed to draw any reliable conclusions about the relevance of our findings to humans," Prof Zierath added, commenting on the study published in the PNAS journal.
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Previous studies have reached similar conclusions, while also discovering differences between the best time to exercise for men and women, depending on their goals.
For example, women who want to lose weight should exercise in the morning, while those who want to build muscle should work out in the evening, according to one US study.
But while women burned more body fat by working out in the morning, men saw more benefits from evening exercise.
Although the exact reasons for the findings were unclear, authors from the study suggested it could be partly due to differences in hormones, biological clocks and circadian rhythms.
The researchers also said women may burn more body fat in the morning because they are more likely to have excess belly fat. Meanwhile, other research suggests that morning exercise can reduce motivation for food, challenging the assumption that you 'work up an appetite'.
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It should be noted that all participants who took part in and stuck to the US study improved their overall health and performance during the trial, regardless of when they exercised.
"The best time for exercise is the best time you can do it and fit it into your schedule," Dr Paul Arciero, lead study author and professor of health and human physiological sciences at Skidmore College, New York state, told the BBC at the time.
However, he suggested there is "something else going on", which may mean the ideal time of day to exercise varies depending on what you want to achieve, and differs for men and women.
Women wanting to reduce fat around their middle and reduce blood pressure should aim to exercise in the morning, Dr Arciero explained in more detail. Losing tummy fat is important because it can surround the body's internal organs, like the liver, which can be dangerous.
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However, for women wanting to improve muscle strength in their upper body, as well as their overall mood and food intake, they should exercise in the evening, he added.
While the men in the trial were less affected by the time they worked out, with their strength improving in both mornings and evenings, the latter was found to be "ideal for men interested in improving heart and metabolic health, as well as emotional wellbeing".
Losing weight, exercising regularly, eating a healthy and balanced diet, stopping smoking and cutting down on alcohol can all help prevent or reverse 'metabolic syndrome'.
This is the medical term for a combination of diabetes, high blood pressure (hypertension) and obesity, which can put you at greater risk of getting coronary heart disease, stroke and other conditions that affect the blood vessels, according to the NHS.
In the study, some 30 women and 26 men – all non-smokers, healthy and between 25-55 years old – underwent a supervised programme of exercise for 12 weeks. This included a mix of stretching, sprint, resistance and endurance training.
They were assigned either early morning sessions (between 6.30-8.30am) or evening sessions (6-8pm), completing a different routine each day, for four days a week, all of which lasted less than an hour except for endurance, which was performed for an hour or longer.
Men and women in both groups were provided with meal plans designed by dieticians.
Researchers tested everyone's blood pressure and body fat throughout the study, along with their flexibility, strength and aerobic power, observing any changes.
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The study – published in Frontiers in Physiology – tracked people with a healthy weight, but researchers also say the programme could be beneficial on people who are overweight or obese. "They have more to benefit," said Dr Arciero.
While the research was relatively small, as most studies in this field have so so far been based on just men, the findings are still significant – though more needs to be done to understand the differences between the sexes better.
Additional reporting PA (Karolinska Institutet and the University of Copenhagen study).