Consistent exercise timing may lead to more physical activity among adults with obesity
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SAN DIEGO — Exercising at a consistent time may encourage adults with obesity to participate in regular moderate to vigorous physical activity, according to a speaker at ObesityWeek 2022.
Leah M. Schumacher, PhD, assistant professor in the department of kinesiology in the College of Public Health at Temple University, presented findings from a small pilot study in which adults with obesity and a low activity level at baseline participated in three exercise arms for 3 weeks each: consistent morning exercise, consistent evening exercise and exercise during time of choice. At the end of the trial, participants engaged in more physical activity sessions and minutes when assigned to exercise in the morning or evening vs. choosing when to exercise.
“Prescribed consistent exercise timing in a free-living setting was feasible and acceptable,” Schumacher said. “Interestingly, while the choice was most preferred, it looked like exercise or physical activity was highest in the morning or evening conditions. This is a small sample, so we want to take it with a grain of salt, but in the final visit, a few people mentioned when they had a set time, they felt accountable to be doing exercise, and if they didn’t do it that day, they felt guilty.”
Potential benefits of consistent exercise timing
Consistent exercise timing could be beneficial for several reasons, Schumacher said. Exercising at the same time could be habit-forming and the arrival of exercise time motivational. Planning a particular time to exercise could also help make it a priority and eliminate lack of time as a perceived barrier.
Two recent observational studies linked consistent exercise time to more physical activity. In a study published in 2019, 375 adults who were members of the National Weight Control Registry and maintained a weight loss of at least 30 lb for 1 year or more participated in annual surveys on exercise timing, physical activity levels and exercise habits. About 68% of respondents said they had a consistent exercise time, and those who had a consistent exercise time participated in physical activity for more days and minutes per week than those who had variable exercise times.
A second observational study published in 2021 similarly surveyed adults in the National Weight Control Registry who maintained their weight loss and physical activity habits. This study also found adults who exercised at a consistent time had greater physical activity levels than those who had a variable exercise time. Additionally, at 1-year follow-up, those who consistently exercised in the morning had a stronger exercise habit than evening exercisers.
Prescribed exercise time linked to more physical activity
To build on these earlier findings, Schumacher and colleagues conducted a randomized crossover trial with 15 adults with obesity and low activity levels at baseline. At baseline, 1 week of accelerometry data was collected and a psychoeducational session was conducted to gauge physical activity intention and interest. Participants were randomly assigned to 15 minutes daily of prescribed morning exercise, prescribed evening exercise, or choice of time for exercise for 3 weeks. Adults took part in all three arms, with a 2-week washout period with no physical activity in between each arm. Data were acquired through a hip-worn accelerometer, and email surveys were conducted each night to obtain self-reported physical activity data.
Of the cohort, 80% completed all three arms of the trial. According to accelerometry data, 64.2% of physical activity sessions were completed in the assigned time window, and a greater percentage of adults completed their prescribed exercise during the morning condition compared with the evening condition (74.3% vs. 56.2%; P < .001). According to self-reported data, 85.9% of sessions were completed in the assigned time window, with a higher proportion of adults adhering to their assigned time in the morning vs. evening (89.9% vs. 82.2%; P = .03).
When the participants were asked what their preferred arm was, 50% said they preferred to choose their own time vs. being prescribed morning exercise or evening exercise. However, when physical activity was measured through accelerometer data, adults performed more physical activity bouts and minutes per week when assigned a morning or evening exercise time compared with choosing their own exercise time.
“Consistent exercise timing may be a useful strategy for promoting physical activity in the context of weight management,” Schumacher said. “It’s also a strategy that could be incorporated into broader interventions very easily.”
Several barriers for not performing physical activity were identified. Participants assigned to morning and evening exercise cited being too tired and scheduling or last-minute conflicts as barriers, whereas oversleeping was a more common barrier in the morning arm and “did not feel like it” was more common in the evening arm.
Some limitations of the pilot study included a small sample size, homogenous samples and self-reported measurements of physical activity.
“At this point, we really need larger randomized trials to look at whether consistent timing has a causal impact on physical activity adoption or maintenance,” Schumacher said. “In those studies, it would also be important to look at mechanisms of action like habit or planning. And as a few other people have mentioned, it’s important to look at potential individual differences that might be useful for optimizing timing prescriptions; for example, things like chronotype or lifestyle factors that may make certain times more or less possible.”
References:
Schumacher LM, et al. J Phys Act Health. 2021;doi:10.1123/jpah.2021-0135.
Schumacher LM, et al. Obesity. 2019;doi:10.1002/oby.22535.
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Schumacher LM. Consistency of physical activity timing: Implications for interventions for the treatment of obesity. Presented at: ObesityWeek; Nov. 1-4, 2022; San Diego.
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