Here's a depressing thought for anybody who's hit the gym to lose pounds: working out can actually make you gain weight.

The reason for this is pretty simple. When you exercise your appetite increases. But if you eat much more than you typically do you're just going to offset those calories you burned while working out or worse.

"Appetite often soars when you exercise a lot," explains sports dietitian Linia Patel says. "You need to make sure you eat enough, but stop before you get to the point where you aren’t burning excess energy off."

Among the biggest excess calorie culprits are energy bars and sports drinks. What many people don't realize is that the sugary snacks are designed for workouts of over 90 minutes, not for the typical 45-minute-or-so gym session.

Besides avoiding energy bars and sports drinks, experts suggest not eating at all two-to-four hours before a workout, since the body never does a good job breaking down calories consumed right before exercise. It is for this reason working out first thing in the morning is recommended.

Another tip for those who want to use the gym to lose weight is to focus on cardiovascular work rather than weight training.

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