According to The Daily Mail, the part of the people who spend lunchtime in the walls of the office, the work efficiency in the afternoon increases, in contrast to those who prefer to eat outside of the office. Those who dines in the city, after a break for lunch, come on workplace sleepy and with low activity. In their case, the brain activity is reduced, which affects the quality of work.
The representative of the Humboldt University, argues that the lunch break outside the workplace relaxing. And when one is dealing, for example, with the computing process, it's risky. Although if a person's creative work is quite useful.
These two types of lunch break in the office and outside of it, are quite different from each other, because in the second case there is a change of scenery, no time restrictions, etc.