The Relationship Between Time of Day of Physical Activity and Obesity in Older Women

Abstract

Background Physical activity is important for maintaining healthy weight. The time of day when exercise is performed—a highly discretionary aspect of behavior— may impact weight control, but evidence is limited. Thus, we examined the association between the timing of physical activity and obesity risk in women. Methods A cross-sectional analysis was conducted among 7157 Women’s Health Study participants who participated in an ancillary study begun in 2011 that is measuring physical activity using accelerometers. The exposure was percentage of total accelerometer counts accumulated before 12:00 noon and the outcome was obesity. Results Mean (±SD) BMI among participants was 26.1 (±4.9) kg/m2 and 1322 women were obese. The mean activity counts per day was 203,870 (±95,811) of which a mean 47.1% (±11.5%) were recorded in the morning. In multivariable-adjusted models, women who recorded <39% (lowest quartile) of accelerometer counts before 12:00 noon had a 26% higher odds of being obese, compared to those recording ≥54% (highest quartile) of counts before noon (Ptrend = 0.02). Conclusions These study findings—that women who are less active during morning hours may be at higher risk of obesity—if confirmed can provide a novel strategy to help combat the important health problem of obesity.

Relationship of Consistency in Timing of Exercise Performance and Exercise Levels Among Successful Weight Loss Maintainers

“…Among those who reported a temporally consistent PA routine, early morning was the most common time that exercise was performed, followed by evening. In contrast with our hypothesis and previous work , the particular time of day at which temporally consistent exercisers most often performed PA was not differentially related to PA levels. Our findings thus add to the mixed literature on the optimal time of day, if any, for PA. Because all temporally consistent exercisers in the present study reported, by definition, exercising at the same time day to day, it is likely that these individuals had well‐established PA routines.…”

“…Thus, participants exercising 2 d/wk had to report both exercise sessions within the same time window to be categorized as temporally consistent, individuals exercising 3 d/wk had to report ≥ 2 exercise sessions within the same window, individuals exercising 4 d/wk had to report ≥ 3 exercise sessions within the same window, and so on. This categorical timing scheme was modeled off of prior studies . However, as noted, we further differentiated early‐ and late‐morning exercisers because of potential biological and behavioral benefits of early‐morning PA.…”

“…In addition to the potential importance of temporal consistency or inconsistency for PA levels, the particular time of day that PA is performed might also have implications for weight management. While research in this area has been limited, one study found that older women who were more active in the morning were at lower risk for obesity , and another found that adults who performed a greater proportion of their PA in the morning more successfully increased PA prior to bariatric surgery . Although these findings are initially supportive of the importance of morning PA, there is a need for additional research.…”

Greater Adherence to Recommended Morning Physical Activity is Associated With Greater Total Intervention-Related Physical Activity Changes in Bariatric Surgery Patients

“…In the Women’s Health Study, participants who performed less PA during the morning had higher odds of obesity versus those who performed more, suggesting morning PA assists with weight control. 15 Morning PA might also positively impact body weight and energy to perform PA by improving nocturnal sleep patterns via increased parasympathetic nerve activity and circadian rhythms through increased light exposure. 16–18 Additionally, morning PA, particularly in the fasted state, may contribute to improved metabolic control on the day of and day after exercise.…”

Opportunities and Challenges for Environmental Exposure Assessment in Population-Based Studies

“…Collecting accelerometer data over multiple days allows researchers to assess patterns of behaviors (time of day and variability across days) in new ways so that more precise activity prescriptions (e.g. how much, when, and what behavior) can be given (66, 67). It is also possible to assess physical activity and related behaviors using Global Positioning System (GPS) derived coordinates on individuals, which are now omnipresent on mobile phones.…”