From Fiona Haynes,
Your Guide to Low Fat Cooking.
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Conventional wisdom on dietary fats has changed. Once, all fats were deemed unhealthy, and responsible for all manner of diseases, from cardiovascular disease to diabetes. But years of research have changed our thinking. We now start with the premise that all fats are not created equal—that there are good fats, bad fats, possibly-not-so-bad fats, and very bad fats. Let's take a closer look:

The Good: Unsaturated Fats

As oxymoronic as it sounds, there are actually good fats—the unsaturated kind that help fight the very diseases that consuming excess fat was said to cause. These unsaturated fats are divided into monounsaturated fats and polyunsaturated fats, and both types are thought to have beneficial effects on cholesterol levels.

Monounsaturated fats help lower LDL (bad) cholesterol while also boosting HDL (good) cholesterol.

Polyunsaturated fats are also thought to help lower total and bad cholesterol. But monounsaturated fats tend to be favored over polyunsaturated fats because some research suggests that polyunsaturated fats are less stable, and can reduce levels of good cholesterol as well as bad.

But let's not ignore polyunsaturated fats. These are often a good source of omega-3 fatty acids, found mostly in cold-water fish, nuts, oils and seeds, and also in dark leafy greens, flaxseed oils and some vegetable oils. One kind of omega-3 fatty acid is an "essential fatty acid," which cannot be manufactured by our bodies, so eating these foods is the only way to get them. Omega-3 fatty acids are thought to lower blood pressure, combat LDL (bad) cholesterol, fight inflammation and protect the brain and nervous system.

• Heart-Healthy Walnuts
• The Benefits of Eating Fish
• What are Omega-3 Fatty Acids?

Most cooking oils are made up primarily of unsaturated fats. When it comes to choosing cooking oils, each type of cooking oil varies in its ratio of monounsaturated to polyunsaturated fats. Two oils stand out for their high levels of monounsaturated fats: canola oil and olive oil. Other than nonstick cooking spray, these two oils should be in your pantry.

• Do Cooking Oils Contain Saturated Fat?
• Heart-Healthy Canola Oil
• What is Enova Oil?
• Is Extra-Light Olive Oil a Low-Fat Cooking Oil?

At the end of the day, a good fat is still a fat in terms of calories. Any labels on cooking oil that describe the oil as "light," are referring to the taste or color, not the fat or calorie content. All oils are 100 percent fat and are worth around 120 calories per tablespoon.

The Bad: Saturated Fats

Then there are the bad fats—those artery-clogging saturated fats from meat and dairy products. These fats are solid at room temperature. Saturated fats not only clog our arteries, they also directly raise total and LDL (bad) cholesterol levels. Avoid them as much as possible.

• What are the Main Sources of Saturated Fat?
• Yes or No to Cheese?
• Butter vs. Margarine

But, we are told, some saturated fats may not bad at all: some argue that coconut oil and palm oil may actually be beneficial because their particular fatty-acid make-up means they are metabolized differently in the body. So it could be that plant-based saturated fats may be more beneficial, or at least more neutral, than we think, but there is no broad consensus on this yet. And while coconut oil and palm fruit oil have been rehabilitated in the eyes of some, there are fewer proponents of palm kernel oil.