Evening Exercise: Impact on Sleep and Appetite

Research Overview

Researchers have explored the effects of evening exercise on sleep quality and appetite, specifically focusing on high-intensity interval exercise (HIIE). There is a prevalent belief that exercising before bedtime can disrupt sleep, which may also influence appetite and caloric intake. This raises an important health question: does evening exercise truly interfere with sleep?

Key Findings

The findings from this study suggest that exercising in the evening does not necessarily keep individuals awake; in fact, it may reduce late-night snacking. A team of scientists from Australia conducted this research, which was published in *Experimental Physiology*.

Study Participants and Methodology

The study involved 11 inactive and overweight men, with an average age of 49 years and a mean body mass index (BMI) of 28. This demographic is likely to benefit from high-intensity interval training. Specific criteria for participation included being a non-smoker, engaging in less than 150 minutes of moderate-intensity exercise per week, and having no previous or current sleep or metabolic disorders.

Participants underwent three randomized trials over three days, performing 30 minutes of HIIE at different times: morning (6 AM-7 AM), afternoon (2 PM-4 PM), or early evening (7 PM-8 PM). Each trial focused exclusively on one time of day for exercise.

The HIIE regimen consisted of 60-second sprints on a stationary bike, interspersed with 240 seconds (4 minutes) of recovery, repeated six times to complete the 30-minute session.

Impact Assessment

To evaluate the effects of exercise on sleep, participants used a take-home device for polysomnography (PSG) measurement and actigraphy for sleep monitoring. For appetite assessment, blood samples were collected before and after exercise to measure hormones related to appetite, such as ghrelin.

Results on Sleep and Appetite

The research indicated that the timing of HIIE did not significantly affect sleep quality, including total sleep time, sleep efficiency, sleep onset latency, or wake after sleep onset. In comparison to morning exercise, both afternoon and evening sessions led to lower levels of the hunger hormone ghrelin. However, the timing of exercise did not significantly influence food intake in terms of energy, carbohydrates, fats, proteins, sodium, or sugar.

Study Limitations

The authors noted certain limitations, such as the longer fasting period associated with the morning exercise trial (10 hours) compared to the afternoon and evening trials (3 hours). This discrepancy might have influenced hormone levels. Additionally, factors such as eating and sleeping behaviors could have affected energy intake just as much as the timing of HIIE.

Conclusion

The implications of this study suggest that evening exercise does not negatively impact sleep and may even assist with weight management by decreasing appetite. Therefore, individuals should feel encouraged to incorporate evening workouts into their schedules if it suits their lifestyle.

Reference

Larsen et al. “Evening high-intensity interval exercise does not disrupt sleep or alter energy intake despite changes in acylated ghrelin in middle-aged men.” *Experimental Physiology*. https://doi.org/10.1113/EP087455