The effects of alternate‐day fasting on sleep and physical activity in poor sleeping adults: A randomized control trial

Utilizing a randomized control design, 42 healthy adults (22.5 ± 2.8 years) participated in alternate-day modified fasting over a 12-day treatment period. Assessments of sleep included sleep time, efficiency, latency and wake after sleep onset, and assessments of physical activity included steps, energy expenditure, sedentary time, time spent in light physical activity and time spent in moderate-to-vigorous activity. Additional measurements included body composition and mood. The alternate-day modified fasting group consumed 25.8% ± 0.3% fewer calories compared with the control group (p = 0.03). There were no differences between groups for change in body mass index (p = 0.87), total fat mass (p = 0.91) or total lean mass (p = 0.88). Daily energy expenditure did not differ between groups (p = 0.11). On fast days, participants spent 34.5 ± 12.7 more minutes sedentary (p = 0.01), took 1100 ± 362 fewer steps (p < 0.01), and engaged in 27.2 ± 8.4 fewer minutes of moderate-to-vigorous physical activity (p = 0.00) compared with non-fasting days. Sleep duration, efficiency, latency or wake after sleep onset were not different between conditions (p = 0.92, p = 0.10, p = 0.09 and p = 0.66, respectively). We conclude that alternate-day modified fasting does not alter sleep time, efficiency, latency or wake after sleep onset in people reporting poor sleep quality, and does not alter overall physical activity. Although average daily physical activity is not altered, fasting in this manner does tend to result in more sedentary time and less physical activity with compensation on non-fasting days.