Moderate to vigorous physical activity during the morning hours, from 7 to 9 a.m., appears to be the most favorable for fighting obesity, according to an analysis published in the Obesity Society’s journal Obesity.

The researchers point out that previous research has focused on the frequency, intensity and duration of physical activity, but few have investigated the diurnal pattern of accelerometer-measured physical activity to classify the time of day when human movement occurs.

In the present research the scientists investigated whether the daily pattern of the accelerometer measured mmoderate to vigorous physical activity influences the association between human movement and obesity. They used data from 5,285 participants and physical activity was classified into three categories, morning, noon, evening.

The results revealed a strong relationship between activity and obesity in the morning group. Participants in this group had lower body mass index and waist circumference than those in the other groups. They also had a healthier diet and less daily energy intake per unit of body weight compared to the other groups.

Overall the participants in the morning group were 10-13 years older than the other two groups. They also had the highest proportion of women, were predominantly non-Hispanic white, had a college or higher education, and had never used tobacco or alcohol.

Clinical psychologist Rebecca Krukowski clarifies, however, that “it is not known whether people who exercise regularly in the morning may differ systematically from those who exercise at other times, in ways that were not measured in this study.” As he adds, those who consistently wake up early enough for morning exercise “may be biologically different from ‘night owls’.”