Friendly Fats -- and Fiendish Ones

Fats get a bad rap.

Many people think they're all unhealthy when, in reality, many have lots of nutritional value, as registered Dietician Cynthia Sass pointed out on "The Early Show" Thursday.

And that matters a lot, since about a-third of our calories each day should come from fat.

So, which ones are the best?

Sass, co-author of "The Ultimate Diet Log," (read an excerpt) served up the facts on fats:

It may seem counterintuitive, but eating more fat is one of the best strategies for slimming down and staying healthy.

Fat is one of the most important nutrients in your diet. It's a structural part of every cell membrane in your body, which means you can't heal a cell or construct a new one without this key building block. Fats also are a component of skin and hair, and certain types of fats are essential for controlling blood clotting, keeping your brain healthy, and fighting inflammation in your body. Without fat, you wouldn't be able to absorb certain antioxidants and the fat-soluble vitamins -- A, D, E and K -- that "hitch a ride" with fat to get transported from your digestive system into your blood. In my private practice, I have fat-phobic clients who cut their fat intakes too low and, as a result, experience fatigue, dry skin, dull hair and irregular periods -- these are corrected once they start eating enough "good" fat.

All fats have the same number of calories (9 per gram compared to 4 per gram in protein and carbohydrate), but choosing low-fat foods isn't the best recommendation.

Some of the healthiest foods on the planet are high in fat -- such as extra virgin olive oil, avocados and almonds.

The key is to eat smaller portions of healthy, high fat foods. For instance, low-fat peanut butter typically has 10 fewer calories per serving (sometimes the same number of calories), but it has more sugar. When they remove fat, they have to fill its space. Choose all-natural, full-fat peanut butter and other unprocessed, whole foods that contain plant-based fats.

But not all fats are created equal! Some are good and some are bad.

There are four main types of fat in food:

Saturated
Trans or partially hydrogenated
Monounsaturated (aka MUFA)
Polyunsaturated (aka PUFA)

SATURATED FATS

Saturated fats, from animal-based foods like whole-milk dairy products and fatty cuts of meat, are known as one of the bad guys. They've been linked to upping the risk of heart disease by clogging up arteries and boosting levels of "bad" HDL cholesterol. A recent study also found that animal-based saturated fats tend to override the body's satiety mechanism, the "I'm full" signals.

But there are a few exceptions - fortunately, two of the most delicious! Recent studies have confirmed that saturated fats from dark chocolate and coconut are healthful. Coconut oil has been show to increase "good" HDL cholesterol levels, boost calorie and fat=burning, and help reduce dangerous belly fat. And a relatively large percentage of the saturated fat in cocoa gets converted to a heart-healthy monounsaturated fat that lowers LDL and raises HDL. And because both cocoa and coconut are plants, they're also rich in antioxidants.

TRANS-FATS

There's no good news here! Man-made trans-fats, found in foods like crackers, cookies, baked goods and fast food, is crafted from partially hydrogenated oil, which means liquid oil that had hydrogen added to it to make it solid. It's been shown to boost weight gain and belly fat even when the exact same number of calories are consumed and the percentage of total fat is identical. Trans-fats have also been linked to an increased risk of infertility. One study found that infertility risk jumped by a whopping 73 percent with each 2 percent increase in trans-fat.

Trans-Fat Loophole

Unfortunately, food products can claim to provide zero grams of trans fat if the food contains less than 0.5 grams per serving (to identify this "hidden" trans fat, check the ingredient list for the words partially hydrogenated). And, a product can also be labeled trans-free if it's made with FULLY hydrogenated instead of partially hydrogenated oil. Technically, fully-hydrogenated oils are trans-free, but they're not risk-free. A Brandeis University study found that eating products made with fully hydrogenated oil, a trans-free alternative to partially hydrogenated oil) may lower HDL, the good cholesterol and cause a significant rise in blood sugar (about 20 percent). At least, that's what the 30 healthy subjects the researchers studied experienced - in just four weeks' time. The best way to avoid both partially- and fully-hydrogenated oils is to eat as many unprocessed or minimally processed foods as possible. For example, choosing liquid oil as opposed to margarine, and nuts and fruit as a snack instead of something that comes in a bag or box.

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