Is lunch the only reason you feel sleepy afterward?

Our body clock produces the greatest sleepiness at night, but it also creates a small dip between 1 and 3 p.m. In experiments, even people who skipped lunch showed reduced concentration and slower reactions at this time. If you did not get enough sleep the night before, the dip becomes deeper. This is also the time of day when your eyelids often feel especially heavy in an afternoon meeting or behind the wheel.

When food arrives, the body shifts toward resting and digesting. Animal experiments have also found that a rise in blood glucose quiets the neurons that produce orexin, a substance that helps us stay awake. So eating more at one sitting brings stronger sleepiness. People often say blood rushes to the stomach and less reaches the brain, but blood flow to the brain stays almost the same after a meal. Feeling dull after eating is less about missing blood and more about the signals that keep you awake easing off for a while.

Many people reach for chocolate or a sweet drink to perk up when they feel sleepy. But a 2019 analysis pooling 31 studies and 1,259 people found no mood boost from sugar at any point after eating it. In fact, within an hour of eating it, people reported feeling more tired and less alert than those given a sugar-free dummy. Despite the feeling of 「my blood sugar dropped, so I'm sleepy」, sweets may briefly add to afternoon drowsiness rather than clear it away.

Try a slightly smaller lunch and a walk of about ten minutes in a bright place afterward. Sunlight and movement both raise alertness. If you really need a rest, a short nap of no more than 20 minutes can also help. Sleeping longer can take you into deep sleep and leave you groggier when you wake. If you still feel overwhelmingly sleepy every day, it may be worth looking separately at whether you are short of sleep or whether something else is causing it.