The skinny on fat is simple enough: Americans eat too much of it, and as a result, wear too much of it.

Today we're eating fewer fatty meats, whole dairy products and other foods rich in saturated fats — the kind that most significantly raise cholesterol, clog arteries and contribute to increased rates of the heart disease that claims one American every 33 seconds. In fact, Americans are consuming a noticeable 18 percent fewer calories from fat than we did 20 years ago. But as a nation, we're actually getting fatter and eating more overall calories than ever before.

One reason might be our reliance on "low-fat" and "fat-free" labels. Today, nine in 10 Americans regularly buy lower-fat versions of food products, which sometimes contain more calories (albeit fewer fat calories) than the original versions.

Problem 1: Less fat can mean more calories.

Some "no-fat" or "low-fat" products contain as many calories as their original versions per serving; a handful can even have a few calories more. Many people consume larger quantities of low-fat foods, believing that they are "healthier." But a 10 or 15 calorie difference per cookie can tip the scales (and not in your favor) if you overindulge. So it's important to read the entire food label, not just the information on fat.

Problem 2: Oils that foil your cholesterol-lowering attempts.

More calories aren't the only concern in low-fat foods. Because of the ingredients in these products, they can raise blood cholesterol levels as much as fattier versions and may have an even more detrimental effect on blood lipids in some people. That's because these lower-fat versions may contain oils that undergo a chemical process known as "hydrogenation," in which a liquid vegetable oil that's naturally high in unsaturated fatty acids (and therefore heart-healthier) is transformed to a more solid and saturated form.

Cheaper To Use

Food manufacturers do that for several reasons. Adding hydrogen to these oils gives foods more texture and a more "spreadable" consistency. The products also have a longer shelf life, and these oils are cheaper to use than more expensive and artery-clogging spreads such as butter and lard.

But this hydrogenation changes oil in two ways: Besides making oils more saturated, it creates trans fatty acids — molecules that get twisted and out of shape during heating. These trans fats can raise the levels of low-density lipoproteins (LDLs), the so-called "bad" cholesterol, sometimes as much as saturated fats do in some people. Meanwhile, trans fatty acids do not increase levels of high-density lipoproteins (HDLs), the "good" cholesterol that is responsive to monounsaturated fatty acids found in olive and canola oils. And some studies suggest that the chemical change induced in fatty acids by hydrogenation also may affect cell function, thereby increasing the risk of cancer.

Read The Label

Besides checking for calorie count, look at the list of ingredients on snack foods and other baked goods. The words "may contain hydrogenated or partially hydrogenated oils" (usually vegetable shortenings or oils such as corn or safflower) indicate the product is hydrogenated. If the nutrition label lists hydrogenated oils among the first three ingredients, you're better off with a substitute, but not one containing a saturated fat such as palm kernel or coconut oil.