If you're groggy from lack of sleep, remember: The more water-filled foods you eat, the better. They can help you feel full.
Hunger can also often be misinterpreted when you are exhausted. However, don't go overboard on carbohydrates, as they can make you sleepy. Balance you meals with lean protein to keep you sharp.
If you've had a bad breakup or you have stress from job or family, think about whole-grain carbs that boost serotonin levels. Serotonin is the brain chemical that signals calm and happy thoughts.
This is another good time to eat foods with fluid, as being hydrated helps concentration and memory as well as energy levels.
British researchers also found nibbling on a few squares of dark chocolate picks up mood as well.
Another study out of London found caffeinated tea is also helpful when consumed four times daily. Subjects had lower levels of the stress hormone cortisol, compared to those who drank a tea placebo.
What you don't want to do when you're stressed is eat too much junk food, alcohol, chips or ice cream. These items consumed in large quantities may increase stress hormones levels, the exact opposite effect you're looking for.
You'll find more nutrition answers in the July issue of Fitness magazine and the September issue of Prevention Magazine.