Those heading to the gym after work may want to adjust their schedules, research suggests.
A US study on 5,285 middle-aged adults showed exercising between 7am to 9am was the best time for weight loss.
Participants in this category had a lower body mass index (BMI) and smaller waist circumference than people who exercised at midday or in the evening. This was despite them spending more time sedentary than the others.
Scientists said morning exercise may be best because the schedule is easier to stick to and people are less likely to be distracted by phone calls, emails or meetings.
A US study on 5,285 people showed exercising between 7am to 9am was best for weight loss (Stock image)
Dr Rebecca Krukowski, a clinical psychologist at the University of Virginia, said: ‘This is exciting new research that is consistent with a common tip for meeting exercise goals.
‘That is, schedule exercise in the morning before emails, phone calls or meetings might distract you.’
She admitted, however, the results could be attributed to other factors, such as having a more predictable schedule or not having any care giving responsibilities.
She added: ‘Predictable schedules could have other advantageous effects on weight that were not measured in this study, such as sleep length and quality or stress levels.
‘In addition, the “morning larks” who consistently rise early enough for morning exercise may be biologically different from their “night owl” counterparts.’
Studies suggest people who get up earlier have circadian rhythms — or ‘body clocks’ — that run earlier, which could improve sleep quality and ensure a consistent schedule, which can all drive weight loss.
Scientists found people who were early birds were 10 to 13 years older than those in the other two groups.
Most of them also had a college degree and said they had never smoked or used alcohol. They also had healthier diets and ate less than those in the other two groups.
For the study, published today in the journal Obesity, scientists looked at data from the official National Health and Nutrition Examination Survey (NHANES) — which assesses the health of about 5,000 adults and children in the US every year.
They used data from 2003 to 2006, when participants wore fitness trackers — or accelerometers — on their hip for to track exercise for seven consecutive days.
While NHANES still uses fitness trackers, they are now worn on wrists, making comparisons with more recent years less reliable.
In the study, data from the trackers was used to split participants into three groups — morning, or from 7am to 9am, midday, between 11am and 1pm, or evening, from 5pm to 8pm, exercisers.
Scientists then compiled data on the BMI and waist circumference in each group to find out which group was least likely to be obese.
Of the participants, 642 were in the morning group while 2,400 exercised at midday and 2,187 in the evening.
BMI was lowest in the morning group at 25.9 kg/m2 — putting them just above the healthy range of 18.5 to 24.9 kg/m2.
The results were similar between the midday and evening groups, which had a BMI of 27.6 and 27.2 kg/m2 respectively — putting them in the overweight range.
Waist circumference was also lowest in the morning group at 36inches (91.5 centimeters).
In the evening group it was 37.4inches (95cm) and in the midday group it was 37.7inches (95.8cm).
Dr Tongyu Ma, an exercise physiologist at Franklin Pierce University in New Hampshire, added: ‘Our findings propose that the diurnal pattern of moderate to vigorous physical activity could be another important dimension to describe the complexity of human movement.’
Researchers are divided on the best time of day to exercise in order to boost weight loss, but several studies point to the morning being the best.
A 12-week study involving 100 adults from Skidmore College, New York, that was published last year suggested women interested in losing fat were best off exercising in the morning.
Another paper from Sweden’s Karolinska Institute published earlier this year also suggested exercising in the morning was best for weight loss, after finding mice had a higher fat metabolism when exercising early in the day.