A stressed and busy lifestyle makes it easy to forget some important basics that should help you revive your energy. "My first question would be, how much water are you drinking? One of the first symptoms of dehydration is being lethargic," says Julianne Koritz, RN, LDN, a dietician in private practice in Boca Raton, FL. Koritz suggests drinking "four twenty-ounce bottles through the day. Morning, afternoon, one at three or four-when people mainly get lethargic-and one at dinner."

Coffee or tea isn't necessarily a good substitute; as Koritz points out, "caffeine is dehydrating." Also, she says, "fresh fruits between meals are better than a power bar or granola bar because the sugar in that bar can cause dehydration. Fresh fruit is not just glucose, it's a natural fructose, which you absorb slower to keep energy levels up."

Greens will also do the trick, says Koritz. "Vegetables, raw or cooked, it doesn't matter. Also, add a bit of protein, perhaps tofu or hummus." For a quick, on-the-go boost, she suggests pistachios, pecans or walnuts, noting that nuts, period, are the best pre-packaged snack.