Your internal body clock, or ‘circadian rhythm’, can explain why you feel so sluggish after lunch. The circadian rhythm is controlled by a tiny region at the base of the brain called the suprachiasmatic nucleus (SCN), which makes us feel sleepy in the evening by sending a signal to the body to release the snooze-inducing hormone melatonin, which also lowers our body temperature.
However, we also experience a miniature version of this process between around 2pm and 4pm. The reason for this isn’t clear, but research suggests that some aspects of our circadian rhythm have a 12-hour cycle, as well as the primary 24-hour one.
The feeling of fatigue can also be intensified by other factors, such as eating a carb-heavy lunch, not getting enough sleep the previous night, or being dehydrated. If you’re really struggling, a post-lunch nap isn’t such a bad idea. Studies have shown that a 20- to 30-minute snooze can boost alertness, attention and mood, and there are even companies who have invested in workplace sleep pods for their staff.
That’s not feasible for everyone, though. So another option is to go for a lunchtime stroll. Light has a big effect on our circadian rhythm, helping to calibrate the SCN, so a good dose of sunshine can be just as effective as a nap at setting you up for the afternoon.