Before you throw that jar of fat-free mayo or those fat-free muffins in your shopping cart, thinking they'll help you lose weight, consider this -- fat does not make you fat.

It sounds like a paradox, but in fact, it makes perfect sense. Fat on your body does not come from the fat that you eat. It comes from calories you consume in excess of what you use up with activity.

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All food that you eat is digested and turned in to basic units of energy called glucose. Glucose energy translates into calories. And unused calories are stored as body fat. It doesn't matter what type of food the calories come from, they all are either used or stored as fat.

Fat has a fattening reputation because, of all the food types, it is the densest source of food energy. So just a little bit of fat packs a big calorie punch. And since fat also tastes good, it's easy to overload your diet with extra fat calories. The consequence could be weight gain, or maybe just not the weight loss you were expecting. In this way, fat in your diet does affect fat on your body.