Some people prefer to work out on an empty stomach; some like a pre-workout snack. Which burns more calories, and which has the most impact on your performance? It depends. While exercising on an empty stomach may burn a few extra fat calories, research shows that total calorie burn is about the same, and that's all that matters when you're trying to lose weight.

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If you're not sure if you should eat before a workout, then give it a try. Eat a snack of about 200 calories one to two hours before your workout. A carbohydrate-protein combo works best - think string cheese and an apple or peanut butter and whole-grain crackers. Then notice how you perform during your workout. Can you work out at a higher intensity for a longer duration? Note when you get tired and when you run out of steam - also note if you have cramps or other gastric issues. Then try the same workout on an empty stomach. Do your efforts backfire because you run out of energy, or are you able to keep going?