Look at the nutrition panel of a cereal box, an energy drink or even a candy bar, and you get the impression that we humans are flesh-covered automobiles: Fill us up with energy (otherwise known as calories) and we'll cruise along until we hit the next filling station.

But if feeling energetic really is that simple, why do so many of us feel exhausted, stressed and perpetually ready for a nap? Because, explains Robert E. Thayer, Ph.D., a mood scientist and professor of psychology at California State University, Long Beach, we're going about stoking our energy all wrong. By using food to fix our draggy moods and low energy, we're letting our emotions rule our bodies, and we're getting fatter in the bargain. If we instead find ways to energize ourselves out of low moods that don't involve food, we'll break free of the tyranny of overeating.

Thayer's book, Calm Energy: How People Regulate Mood With Food and Exercise, recently released in paperback (Oxford University Press, 2003), presents this startling but ultimately convincing argument: Everything flows from your energy Â- not only better moods and the ability to control overeating, but even your deepest feelings about yourself and your life. "People think of self-esteem as a fixed trait, but in fact it varies all the time, and sophisticated tests have shown that when you're feeling energetic, your good feelings about yourself are much stronger," Thayer says.

Thayer outlines levels of energy from "tense tiredness," the lowest or worst level, in which you are both tired and anxious, to "calm tiredness," defined as fatigue without stress, which can actually be pleasant if it occurs at an appropriate time (for instance, just before bed), to "tense energy," in which you're all revved up and doing lots of work, though not necessarily your best. For Thayer, "calm energy" is the optimum Â- what some people call "flow" or being "in the zone." Calm energy is energy without tension; during this pleasant, productive state, our attention is completely focused.

Tense tiredness is the one to watch out for: Your mood is low, you're stressed and you want both a burst of energy and something that will comfort or soothe you. For many of us, that translates to potato chips, cookies or chocolate. Says Thayer: "We're trying to self-regulate with food, when what would help us is the very thing we feel too tired for: exercise."

Here are six steps that can raise energy and help reduce tension:

1. Move your body. "Moderate exercise, even just a brisk 10-minute walk, immediately increases your energy and improves your mood," Thayer says. "It achieves a better mood effect than a candy bar: an immediate positive feeling and slightly reduced tension." And in Thayer's research, study subjects who ate candy bars reported feeling more tense 60 minutes later, while 10 minutes of brisk walking raised their energy levels for one to two hours afterward. More vigorous exercise has the primary effect of reducing tension. Although you may actually experience an energy dip immediately afterward (you're tired from your workout), one to two hours later you'll have an energy resurgence that's a direct result of that workout. "Exercise," Thayer says, "is the single best way of both changing a bad mood and increasing your energy, although it may take time for someone to learn that truth, through experiencing it over and over again."

2. Know your energy highs and lows. Everyone has an energy body clock, Thayer says. Our energy is low immediately after waking (even after sleeping well), peaks in the late morning to early afternoon (usually 11 a.m. to 1 p.m.), drops in the late afternoon (3–5 p.m.), rises again in the early evening (6 or 7 p.m.) and plummets to its lowest point just before bed (around 11 p.m.). "When energy drops at these common times, it leaves people vulnerable to increased tension and anxiety," Thayer says. "Problems look more serious, people think in more negative terms. We've seen this in studies where people's feelings about exactly the same problem varied widely depending on the time of day."

Rather than feeding your anxiety, Thayer suggests paying attention to your body clock (do you peak earlier or later in the day?) and scheduling your life accordingly whenever you can. Plan to take on easier projects when your energy is low. For many people, the time to tackle tough tasks is in the morning. "That's when you're able to really take on a problem," Thayer says. "It's no accident that most food urges and overeating happen in the late afternoon or in the late evening, when energy and mood are low and we're looking for energy enhancement." That's exactly the moment for a brisk 10-minute walk.

3. Learn the art of self-observation. This is such a key skill that Thayer teaches an entire course on self-observation and behavior change at Cal State Long Beach. It's human nature that what happens immediately after an action tends to reinforce that action, he says. Eating always feels good immediately after, though not necessarily for long (guilt and anxiety often come into play, for example), whereas the energy surge from exercise may take a while to become apparent. "What's really important is to look not only at how something makes you feel immediately, but also at how it makes you feel an hour later," Thayer says. So try your own self-study: What effect does caffeine have on you in the morning, afternoon and evening? How about exercise, including intensity, time of day and type of activity? Once you understand your own highly individual responses, you can use your knowledge to overcome your impulses Â- especially your "tense tired" impulses, those that beg for the immediate comfort of sweets and the couch rather than for the more lasting benefits of a good workout or a conversation with a close friend.

4. Listen to music. Music is second only to exercise in raising energy and reducing tension, according to Thayer, though younger people tend to use this method a lot more than older people. Thayer feels that music is underused as a highly efficient method of lifting mood. Try a gorgeous aria, jazz riff, or even hard rock Â- any music you like works.

5. Take a nap Â- but not for long! "Many people don't know how to nap properly, so they say that napping makes them feel worse," Thayer says. The trick is to limit the nap to 10–30 minutes. Any longer will leave you feeling groggy and also keep you from getting a good night's sleep. You will feel low in energy when you first arise from a nap, Thayer cautions, but that will soon dissipate and leave you feeling refreshed.

In fact, not getting enough sleep is a primary reason for our nationwide energy slump; we now average less than seven hours a night, and all the sleep science we have recommends a minimum of eight. "Our whole society has been speeding up Â- we're working more, sleeping less," Thayer says, "and that ends up making us eat more and exercise less."

6. Socialize. When people in Thayer's study were asked what they do to raise their spirits (and consequently their energy level), women overwhelmingly said they look for social contact Â- they call or see a friend, or they initiate social interactions. This can be extremely effective, according to Thayer. So the next time you feel your energy sagging, instead of reaching for chocolate, make a date with friends. Your mood (and your waistline) will thank you.