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They OD on the EVOO
The rationale: "Olive oil is so good for me—I can never have too much of it."

The mistake: Actually, you can, say registered dieticians Tammy Lakatos Shames and Lyssie Lakatos, aka the Nutrition Twins. They find that many of their health-conscious clients think the health benefits of this Mediterranean oil (e.g., heart-healthy monounsaturated fats, flavonoid antioxidants and vitamin E) cancel out its calories. But it's still an oil—one that packs 120 calories and 14 grams of fat per tablespoon. "People will put 300 calories in the pan before they even start cooking," the Nutrition Twins tell us.

Try this: Measure out the oil you use for cooking as well as for dressings or sauces. The Nutrition Twins also suggest putting olive oil in a spray bottle so that a little will go a longer way.