The weird reasons you're so tired: it may not be the heat that has you feeling wilted. Read on for unexpected causes of a summer energy slump.(YOU YOU YOU)

It's summertime, and you'd be loving life ... except that you feel like a slug when your alarm goes off or by midday. What gives? "Plenty of surprising physiological things can drain energy," says Richard Schwab, MD, codirector of the University of Pennsylvania's Penn Sleep Center. "Plus, emotional stress can be just as tiring." Read on to see if one of these sneaky energy zappers could be keeping you from feeling rested.

Summer Fruits

This time of year, fresh produce and lifeguards are equally drool-worthy. Fruit's healthy, but the postsnack crash can leave you dragging. "Certain fruits send your blood sugar sky-high, and what goes up will come down," says Dan Hamner, MD, author of Peak Energy. How quickly a food spikes your blood sugar is measured on the glycemic index (find it at glycemicindex .com). Fruits with GI scores over 55 (like cantaloupe and pineapple) can catapult you into a fructose frenzy.

Fatigue fighter: Dr. Hamner suggests eating some nuts with your fruit--their proteins and fats stabilize blood sugar.

Swimming in a Pool

Playing in the water is one of the joys of summer (again: lifeguards), but the chlorine can irritate sensitive sinuses. And sinusitis can lead to exhaustion and even chronic fatigue.

Fatigue tighter: If you get forehead pressure when you swim, avoid diving (and cannonballing), which shoots water straight up your nose. "Using a nasal saline solution or going to a steam room after your swim can help prevent sinusitis," says Alexander C. Chester, MD, clinical professor of medicine at Georgetown University Medical Center.