These lunches invariably are buffets with wide spreads. So, you end up eating quite a lot. You get back to office around 3 in the afternoon. And post-lunch, you don't feel like working. So, the rest of the day is practically wasted.
The other problem is that there's something about these lunches that make you feel that you're at the weekend. It feels like a Friday or Saturday. So, you get into the weekend mood. For the rest of the day, your mind feels like its about to go into 'weekend mode' and you can hardly bring yourself to start something new.
Some of my colleagues take this to extreme levels. They drink some beer or down a couple of Breezers with lunch. So, they actually don't even get back to office after the lunch to put on the pretense of working as the rest of us do!
These lunches are, however, a good chance to mix with colleagues in an informal atmosphere. This bonding does help in many ways. We have a birthday lunch again tomorrow (Thursday!). Yet another pseudo-long-weekend on its way!