Eat protein and increase your dopamine production, which is a "happy and alert" neurotransmitter (http://frank.mtsu.edu/~studskl/food.html). Going heavy on the carbohydrates spikes your serotonin, and if they're simple carbohydrates your insulin vs. blood sugar will suck the energy right out of your brain in an hour. Ergogenics like Adrafinil are a more extreme and expensive alternative to caffeine, but cheap nootropics like Piracetam or Vinpocetine may do the trick, if dietary changes alone don't.

As other posters have said, avoid starch and sugar.

Walking quite far to lunch is good. Then you have to walk the same distance after lunch.

... And, if it's with a friend/colleague it's a great time to talk and un-muddle your thoughts.

Reduce sugar & other carbs during lunch (replace with protein & fiber as much as possible.)

Instead of caffeine you could try Yerba Mate tea... more brain energy, less jitters.

I second the diet recommendation. It makes a big difference for me when I can manage not to eat sweets and empty carbs.

I just throw down an espresso after lunch and I feel good.

I second the Yerba Mate suggestion. It jolts the mind without giving you that over-caffeinated coffee feeling.

Peppermint tea works for me as well (I must admit -- it doesn't have that true allure of a coffee though).

Do you build the same dependency on it that you do with coffee?

No... it has a different problem: you can use just a little and it'll work, but use too much and you may feel a little anxiety.

Eat less. I've also heard it's good for your health to eat less if you can.

One of the common themes I hear from people who come to the US from overseas is that food portions are quite large here.

Eat, get back to the desk (check email or some low intensity stuff), then about 30 min later, go for a walk. Get out of the building and into sunlight for a minimum of 15-20 minutes. Hot, cold, doesn't matter. Get out and walk.

Somewhat off-topic: I realized recently it's more important when and how you get your caffeine then how much. There's a reason 5 o'clock tea is famous. For me morning caffeine is wasted or worse, and the best time is around 3-5 in the afternoon, or a couple of hours after lunch. Metabolisms differ, of course.

Also I switched to black tea: wider spectrum and longer lasting, but smaller punch. Don't abuse it though, may not feel like it but it's as strong as coffee.

Take whatever you are eating for lunch and immediately cut it in half. Eat the first half and save the rest for as long as you can, eating it ideally 3 hours later. For instance, I eat 1/2 at about 10:30-11am and half at around 1-1:30. You will no longer get the food coma and over the long run it will help you speed up metabolism, lose weight, etc.

You dont! You take a nap.

The United States needs to adopt the siesta! With the proper implementation, the productivity gains could be tremendous!

I know...business partner anyone? Thats a niche market!

On the topic of protein rich lunches; what do people usually do?

I like to take a lunch to the office since the need to eat seems to come up at varying times of the day.