Yesterday's New York Times featured a helpful article on this condition, known as the "post-lunch dip." The good news is that you are not alone. The Times calls the experience "universal," though the paper notes that different people experience the need to nap with differing intensities. If you can't suppress your yawns, its not your lazy constitution that's to blame, however; it's biology.
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. Add the effects of food, which can also induce drowsiness, and an overpowering desire to sleep may result.Some companies where safety is paramount allow workers to nap after lunch (studies show that more car accidents occur during the "dip" than at other times during the day), but with the need for efficiency in the modern workplace that's unlikely to be an option for the vast majority of managers. Besides sneaking off to a storage closet for a ten minute power-nap, or moving to Spain where siestas are the norm, what can be done? Fred W. Turek of the Center for Sleep and Circadian Biology at Northwestern University recommends that workers, "try to perform more mundane tasks during the dip, and save projects that require the greatest accuracy, mental acuity and creativity for other times of the day."
It may also be helpful to exercise your way through the dip. Though if you can barely click your mouse, a nice spin on the elliptical is unlikely to appeal to you. Also, waking up every day at the same time may help stave off the afternoon yawns. Beyond that, the Times can only offer the old standbys: a cup of coffee and a good night's sleep. And of course the consolation of knowing you are not alone and not to blame.