Can you set your watch by your energy slumps? It happens to everyone. In fact, your body clock is part of the problem—when your internal chronometer is out of whack, you feel wiped out. But there are ways to keep your power surging.

7 a.m.: The Morning Fog
When you first awaken, the parts of your brain associated with consciousness begin firing right away. But the part that handles problem solving and complex thought is like a cold engine—it needs time to warm up. And it doesn't help that you also have a nearly empty fuel tank.

The fix: Make a bowl of instant oatmeal prepared with half a cup of skim milk. Tufts University researchers found that people who ate this morning meal got a steady glucose infusion, which increased their alertness all morning. And enjoy a java: A University of Pennsylvania study shows that a dose of caffeine can (no surprise to us) get your mind moving.

1 p.m.: The Lunchtime Letdown
If your lunch consists of carbs à la starch, you're headed for a brain drain. Eating a high-carb meal is the surest way to cause your insulin levels to spike—and your concentration to crash.

The fix: If you can't limit your carbs, work in extra fiber to slow your digestion and the release of insulin. For example, if your lunch includes a baked potato, make sure you eat the skin. And when you give in to a carb binge, snack on grapes or an apple afterward; either fruit will help stabilize your blood sugar.

3 p.m.: The Afternoon Slump
Experts think the afternoon dip in alertness occurs because the drive from the circadian clock to stay awake is not yet strong enough to cancel out the sleep drive caused by having been awake for half the day.

The fix: Try to sneak in a stroll around the block (or at least down the hall). British researchers recently found that when people exercised during their workday—regardless of the duration or intensity of the movement—they were less likely to feel fatigued, and that translated into a 15 percent improvement in job performance.

6 p.m.: The Pre-Workout Conk-Out
You know that working out will leave you energized, but you don't have the energy to work out. In most cases, the problem is simply that you've forgotten a critical piece of exercise equipment: food.

The fix: Schedule a small snack roughly an hour and a half before your postwork workout. The ideal mini meal totals 250 calories and consists of 25 to 35 grams of carbohydrates, 10 to 15 grams of protein, and up to 5 grams of fat.

8 p.m.: The Prime-Time Torpor
There's no complicated biochemical reason for being tired now—you worked all day! But it's early, and even if you don't have plans, falling asleep now will only mess up your body clock and leave you feeling more fatigued in the a.m.

The fix: Instead of turning on the TV, load your iPod with something upbeat and familiar to get you going. Experts say just thinking about upbeat music and hearing it in your mind can give you a boost of energy.

Energy crises solved.