This has nothing to do with lunch or dinner, but with people's biological clocks, which is more accurate for office workers with regular working hours. Most office workers finish their lunch around 12. At this time, they will take a lunch break and be energetic when they go to work in the afternoon. In the evening, we all go home for dinner after work. After dinner, everyone likes to go out for a walk and go to bed around 10 at night. This is just a habit formed by people, and of course it cannot be generalized.

For example, in some construction sites and processing plants, the lunch break is usually one hour. After dinner and smoking, I will start working in the afternoon. For high-intensity work, I don't feel sleepy at all, but it is easier to get sleepy after dinner at night, and I am too tired to sleep.