Good vs. bad fats – how to tell them apart
Published Sep 11, 2007
Everyone knows that eating too much fat is bad for your health, but just as many people know that fats are just plain confusing. There are good fats and bad fats and different types of each. Fats come from both animals and plants – and then there’s cholesterol. No wonder some people just throw up their hands and give up. But it’s not impossible to get a basic understanding of fat. Just keep reading and you’ll be well on your way.
One thing that all fats have in common is the number of calories they produce inside your body; namely, nine per gram of fat eaten. To put that into context, a gram of protein equates to four calories and a gram of carbohydrate is also four. That is the sum total of everything you need to know about calories: fats = 9, protein = 4 and carbohydrate = 4 (calories per gram eaten). But please note well that every gram of fat provides more than twice the number of calories as does either protein or carbohydrate. So as an aside, you can readily see that cutting back fat is more beneficial on a gram per gram basis than cutting back other foods.
Fats come in two major types: bad and good. And each type has two subtypes. Bad fats are saturated and trans, which tend to be solid at room temperature (think of butter and lard), and good fats are mono-unsaturated and poly-unsaturated, which tend to be liquid at room temperature (think of vegetable oils). So if you can actually see the fat, like when you’re shopping, it’s easy to tell bad (solid) from good (liquid). The problem is you can’t always see it, which is why you have to read the label.
First let’s talk a bit about cholesterol, which also comes in bad and good types. We can eat cholesterol â€“ it only comes from animal-derived foods like meat, dairy products and eggs â€“ but even if you are a strict vegan (there’s no cholesterol in plants), your body naturally makes the cholesterol it needs. Bad cholesterol (LDL) is associated with heart and artery disease (heart attack, stroke, atherosclerosis, hardening of the arteries). Good cholesterol (HDL) actually takes cholesterol away from your arteries and takes it to the liver for digestion and removal.
Bad fats (saturated and trans) raise the levels of bad cholesterol. Moreover, bad fat-containing foods also tend to be high in cholesterol (so you get a double whammy: you eat cholesterol and the bad fats raise your cholesterol). Trans fats also lower good cholesterol. Good fats (mono and poly-unsaturated) don’t raise bad cholesterol and, when eaten in moderation, actually are beneficial.
What foods contain the bad saturated and trans fats? Saturated fats most often come from animal sources: meat and dairy products (these also contain cholesterol). Some vegetable oils, like palm and coconut) contain saturated fats (they don’t contain cholesterol). These oils are an exception to the rule noted above that visibly liquid fats are always good. Saturated fats can also be added to processed foods such as cakes, cookies, pies, chips, butter and salad dressings (including mayonnaise). Please also remember that ice cream is a dairy product containing lots of saturated fat.
Trans fats are almost always man-made. They are sometimes listed on food labels as hydrogenated and partially hydrogenated vegetable oil (they actually take good fat and make it bad!). Because trans fats are both bad and hidden (they’re man-made and added to processed foods so you can’t see them), there’s been much effort recently to get rid of them. The types of foods most likely to contain trans fats are cakes, cookies, crackers, pies, margarine, French fries, fried foods, chips, shortening, cereal and candy.
Examples of foods high in monounsaturated fats include vegetable oils such as olive oil, canola oil, peanut oil, sunflower oil and sesame oil. Other sources include avocados, peanut butter, and many nuts and seeds. Foods high in polyunsaturated fat include a number of vegetable oils, including soybean oil, corn oil and safflower oil, as well as fatty fish such as salmon, mackerel, herring and trout. Other sources include some nuts and seeds. The omega-3 and 6 fatty acids are polyunsaturated oils and are the ones contained in the fatty fish just mentioned.
In summary, bad fats are saturated fats (that may also contain cholesterol) and trans fats, both of which raise bad cholesterol. Saturated fats tend to be solid at room temperature and are easy to see when in their solid form, but can also be hidden in many processed foods. Good fats are unsaturated (mono and poly), tend to be liquid at room temperature, and tend to be found in vegetables (including nuts and seeds) and in some fish.
Next time, we’ll take a look at fats in the diet, how much of the different types of fats should you eat and how to figure it all out.
There’s lots of great information on fats and diet at the American Heart Association’s Web site.