Key takeaways
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New research found that adults who routinely exercised moderate to vigorously early in the morning were less likely to be overweight or obese than those who exercised later in the day.
The diurnal pattern of moderate to vigorous physical activity and obesity: a cross-sectional analysis
Aim
Moderate to vigorous physical activity ( MVPA) protects against obesity. However, the optimal time of day to perform MVPA for weight management is controversial. This study is designed to investigate the influence of diurnal pattern of MVPA on the association between MVPA and obesity.
Methods
A total of 5285 participants in the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2006 were cross-sectionally analyzed. The objectively measured diurnal pattern of moderate-to-vigorous physical activity (MVPA) was classified into three groups using clustering analysis. K-means: morning (n = 642); noon (n = 2456); and late (n = 2187). Associations of MVPA level and diurnal pattern with obesity were tested.
Results
A strong linear association between MVPA and obesity was found in the morning group, while a weaker curvilinear association between MVPA and obesity was observed in the midday and evening groups, respectively.
Among those who met physical activity guidelines, the adjusted means for BMI were 25.9 (95% CI: 25.2–26.6), 27.6 (95% CI: 27.1–28.1 ) and 27.2 (95% CI: 26.8–27.7) kg/m2 in the morning, noon and evening groups, respectively, and for waist circumference they were 91.5 (95% CI: 89 .4–93.6), 95.8 (95% CI: 94.7–96.9) and 95.0 (95% CI: 93.9–96.1 cm), respectively.
Conclusions
The diurnal pattern of moderate to vigorous physical activity (MVPA) influences the association between exercise and obesity. The promising role of morning MVPA for weight management warrants further investigation.
Comments
"For people who exercise regularly, their body mass index [BMI] is 2 units lower and their waist circumference is 1.5 inches smaller if they exercise early in the morning than at other times of the day," the study said. Study author Tongyu Ma, assistant professor of exercise physiology at Franklin Pierce University in Rindge, NH. BMI and waist circumference are considered two key measures of obesity risk.
The upshot, Ma said, is that "exercising in the morning is a promising tool for weight management."
To explore the question, the researchers tracked obesity status among nearly 5,300 adult men and women. All were enrolled in the current US National Health and Nutrition Examination Survey, either between 2003 and 2004 or between 2005 and 2006. Each of the participants wore a hip accelerometer every time they were awake for between four and seven consecutive days, including at least one day over the weekend.
Based on activity routines, they were then classified into one of three exercise groups: morning (642 participants), midday (2,456), or afternoon (2,187). In turn, waist circumferences were measured and BMI scores were calculated. BMI is a measurement based on height and weight.
The result: Exercising between 7 a.m. and 9 a.m. was found to be associated with a lower risk of being overweight or obese compared to exercising later in the day. BMI scores revealed that all participants in the study were overweight, meaning their BMIs registered between 25 and 29.9. But while those in the morning group had an average BMI of 25.9, those in the midday and evening exercise groups had an average BMI of 27.6 and 27.2, respectively.
Similarly, although the average waist circumference observed among the morning exercisers was set at approximately 36 inches, that number fell between 37 and 38 inches between the midday and evening groups.
Ma emphasized that for now the research can only point to an association between morning exercises and weight, rather than a direct cause and effect . And in an unexpected twist, the team also observed that those in the morning exercise group actually spent most of their time being sedentary.
But Ma noted that while the morning group may have spent more time on the couch, they probably also had a "more robust morning workout session" compared to the type of activity done by the midday and evening exercisers. evening. "Think about an office worker who exercises every morning versus a janitor who is busy all day. The former probably has a lower risk of obesity," Ma explained.
Another factor: The morning group also tended to eat healthier overall and ultimately consumed fewer calories than their peers in the midday and evening groups.
So what is it about a morning workout that could offer an advantage for staying fit?
Perhaps because "early in the morning, our body is in a low state of emergency after overnight fasting ," Ma suggested. "We don’t have many carbohydrates to burn, therefore our body will rely more on lipids [fats] for "produce the energy needed for exercise. That’s probably why morning exercise may be better for weight control."
The findings were recently published in the journal Obesity .
Connie Diekman is a food and nutrition consultant and former president of the Academy of Nutrition and Dietetics. She agreed that more research is needed to identify what is afoot. But at the same time, she expressed little surprise with the overall findings. "We have long recommended that exercise, first thing in the morning, provides the most benefits," Ella Diekman said. "Up until this point, the evidence has focused on the benefit of exercise in boosting metabolism, which remains elevated once activity is completed, so calorie burn remains higher throughout the day. However, the strength of "The evidence was never strong enough to say, ’You should exercise in the morning.’"
"The most important recommendation from my point of view as a registered dietitian is that to maintain a healthy body, physical activity must be part of our routines," Diekman said. "So, each week try to get at least 150 minutes of physical activity, in whatever way best fits your daily/weekly routine."
Importance of the study
What is already known?
Moderate to vigorous physical activity (MVPA) is inversely associated with obesity.
What does this study add?
- The association between MVPA and obesity is influenced by the diurnal pattern.
- Early morning (07:00-09:00) appears to be the most favorable time of day to enhance the beneficial association between MVPA and obesity.
