Q. Every day after lunch, you find yourself overcome by drowsiness, and you can’t get any work done because you just want to crawl under your desk and go to sleep. Why does this happen?

A. This universal phenomenon, known as the “post-lunch dip,” represents a collision of biology and economics.

It is entirely natural for humans to want to go to sleep about seven hours after they have awakened. But as the internal rhythms of the body call out for rest, the efficiency of the modern workplace demands continued exertion.

Q. What is happening in the body that it craves rest after lunch?

A. First, the 24-hour cycle of the body, or its circadian rhythm, is naturally in a resting phase at this time. In the afternoon, it happens to converge with another physiological cycle — known as homeostatic — that measures the amount of time spent awake and that is also pushing for a rest.