How not to feel drowsy after lunch

How many times have you almost or even fell asleep after lunch while in the office? Personally, it occurred to me a few times but I usually avoid “taking a nap” in the afternoon as I know I would have difficulty trying to sleep later in the night. So, I was curious what causes human to feel so sleepy — especially after lunch and decided to find out more about it.

According to this report, it states that human feels sleepy not because of the lunch but rather, because of our sleep patterns and cycle. Here’s an extract from the article which explains why human feel sleepy at certain time of the day:

Recent research suggests that each day with insufficient sleep increases our sleep debt and, when this sleep debt becomes large enough, noticeable problems appear (Coren, 1996a). These sleep-debt-related problems are most predictable at certain times of the day. This is because the efficiency of our physical and mental functions show cyclic increases and decreases in the form of circadian rhythms. While our major sleep/wakefulness rhythm has a cycle length of roughly 24 hours, there are shorter cycles as well, with the most important of these being a secondary sleep/wakefulness cycle that is around 12 hours.

Because of these cycles, the pressure to fall asleep is greatest in the morning, between 1 and 4 a.m. In addition there is a less pronounced, but still noticeable, increase in sleepiness 12 hours later, between 1 and 4 p.m. It is this afternoon low point that makes you feel sleepy after lunch, not the meal that you may have just eaten. It probably also was the original reason for the afternoon nap or siesta.

However, I came across another article that suggests that feeling sleepy after lunch is due to the food we consumed and it also gave tips on how to survive the second half of your day. So as to say, I’m still confused on what exactly causes human to feel sleepy after lunch and I’m on the search for even better explanation.