The ideal midday meal includes protein and fiber, and isn't too high in refined carbs. On days when that just didn't happen, try a late-afternoon do-over, albeit one that won't ruin you for dinner in three hours. Half of a classic peanut butter and jelly sandwich can do the trick, since it contains fiber and protein . Bonus points for using whole grain bread, low-sugar jelly and PB made from just two ingredients: peanuts and salt.

We know how important it is , but there are days when we're just too distracted to stop and sip, or when we feel like we need caffeine more than we need hydration. Yet dehydration can absolutely contribute to sleepiness . One way to combat that (aside from drinking H2O, that is) is to munch on hydrating fruits and vegetables, whether cucumber slices (they're 95 percent water ) or strawberries (90 percent water ).

It all seemed so doable at 10 a.m., and now, six hours later, you're wondering how you'll ever complete every task you set out to accomplish. As anxiety creeps in, may we suggest...chocolate? And if it's the dark stuff, covering almonds, even better. The chocolate may help you feel less stressed out, and the almonds are one of the most satisfying snacks you can eat.

When you've had an early, or light, lunch and it later sounds like there's a lion growling in your belly, there's a good chance the noise translates to "feed me." Scientists say your best bet is a less energy-dense, high-protein snack like yogurt, which improves appetite control and satiety, and reduces the amount of food you're likely to eat later (just watch the added sugars in low-fat, flavored yogurts). Cottage cheese is another option; it has loads of protein and can be low in fat (look for the two-percent version).

The right pre-exercise snack will give you the energy to attack those hills, to digest easily (so you can avoid cramps) and will not fill you up so much that you don't want to eat a healthy dinner when class is over. Half an energy bar (just not high-fiber, which may cause a detour to the bathroom; and again, check the label for added sugars before you take a bite), one banana, one cup of applesauce or a few chocolate-covered pretzels (the small amount of caffeine and sugar will give you a boost) are ideal foods to keep in your gym bag.