I've always found the habit of eating at one's desk almost insulting.
It is not about the annoyances that at-the-desk-eaters create for their immediate surroundings. Eating creates noise and smell pollution. I don't want to smell your tacos, and I don't want to hear the scratching of a spoon in an empty joghurt cup.
It is also not the thought about hygienic implications. Lots of the food consumed at desks is finger food. I've grown up getting taught to wash hands before eating and to use knife and spoon. The thought that someone changes between food and operating the keyboard, a piece that has been proven to be dirtier than toilet seats, is unsettling.
No, it is the fact that the person sees eating as a mindless task that can be done _while working_ that bothers me most. As if it was filling up gas at the pump. No, eating to me has two dimensions that these cultureless creatures spurn: that food is, next to breathing and sleeping, one of the most important things that keep you alive. You liteeally are what you eat. Your body tells you very directly what it needs and how much. But you got to listen to it while you're eating. It is already a series of sensations that require being mindful. Just think of the texture, smell, and taste of a leaf of basil. Of olive oil. Of fresh fish. Wonderful.
The other side is that eating is a social endeavour. It is an opportunity to bond and build empathy. It's an opportunity to relax and get good ideas as a team. Also to exchange information. I would say those of our team that go out for lunch regularly are more successful than the ones who don't.
So, I think eating at the desk while working is wrong in many dimensions. Taking a walk is definitely a good idea, too.