For entrepreneurs, eating isn't just about satisfying hunger. So say the growing ranks of nutrition experts who specialize in fine-tuning the metabolic performance of business leaders. "You're like an athlete in the workplace," says Richard Chaifetz, CEO of ComPsych, a Chicago-based provider of corporate wellness and employee-assistance programs. "So you should eat like an athlete."

At the very least, that means lots of lean protein, fruits and vegetables, and complex carbohydrates; no processed foods; and minimal white flour and sugar. But when you spend all day confronting challenging mental tasks, the brain's nutritional demands are greater.

For example, have you ever worked so hard that it felt as though your brain were on fire? It sort of was, says Patti Milligan, director of nutrition at Tignum, a consultancy that helps businesses boost employee performance through holistic wellness programs. "You produce lots of oxidants in the brain when you're working," she says. "Foods that are high in antioxidants--berries, beans, apples, tea--act like flame retardants."

And don't forget water. "The brain is 70 to 80 percent water," Milligan says. "When it's metabolically active 10 to 12 hours a day, removing metabolic waste from the brain requires optimal hydration." She suggests "super-hydrating" with two cups at the beginning of the day and avoiding "dehydrators," like processed sugary foods, high doses of caffeine, and soda. And watch out for "brain fog," which can be evidence that you need to hydrate.

Speaking of caffeine, "coffee depletes serotonin, which contributes to a sense of well-being," says Barbara Mendez, a New York City nutrition consultant who works with many business clients. "If you have it on an empty stomach, that quick delivery to the bloodstream leads to more anxiety and stress." So save the coffee for midafternoon, when your hormonal and neural connections often need the boost.

If you do just one thing, cut out fatty foods. Andrew DiMichele, chief technical officer of Omada Health, an online diabetes-prevention program, gave up fries and chips at lunch and found an almost immediate boost in productivity. "A couple of weeks ago, I let this slide, and it was a stark reminder," DiMichele says. "Not only was I sleepy and un-attentive all afternoon, but I was in a miserable mood."

Science bears this out. According to a Cambridge University study, after five days on a high-fat diet, the treadmill performance of lab rats declined by half. Moreover, the rats eating fatty chow began to falter on a maze test they had been trained on--finding only five treats before making a mistake. The healthier rats were able to find six or more treats. And as any entrepreneur knows, it's all about finding the treats.

Brain Food:

Drink Water

A 2011 study in the British Journal of Nutrition found that even mild dehydration in men reduced vigilance and memory and increased tension, anxiety, and fatigue.

Put Down The French Fry

A 2009 Cambridge University study found that high-fat diets made laboratory rats not just slower but dumber.

Sugar = Bad

A recent UCLA study found that a diet high in fructose slows the brain, hampering memory and learning. Omega-3 fatty acids--found in salmon, walnuts, and flaxseed--can counteract the disruption.