For me, it happens around 3 p.m. -- my eyelids get heavy, I find it harder to concentrate and the thought of two more hours of being productive makes my weary head spin. It's called the mid-afternoon energy slump, and it's the pits. What can you do about it? You could take a nap, but that's been shown to cause diabetes. You could mow down on chocolate, but that will quickly ensure that your jeans feel tight by Friday. You could have yet another cup of coffee, but caffeine after three might have you buzzing into the wee hours of the night.

Nope, forget all these. The best solution is exercise.

That's right, research shows that exercise is the best way to fight fatigue. I know, when you're feeling low, the last thing feel like doing is working up a sweat, but it will make you feel a thousand times better. If you're at home, head for a run. If you're at work, a brisk 15-minute walk will do. If you have access to the gym, a short yoga session, game of squash or swim will do wonders.

Exercise not an option? An apple or a handful of nuts will boost your mood without boosting the numbers on the scale. Brushing your teeth will also perk you up.