Q: There always seem to be contradicting reports about fat… Which are “good” and which are “bad”?
A: Fat is present in almost every food we eat – even naturally “fat free” items like carrots and lettuce have trace amounts of fat, which just goes to show you how vital this nutrient is.
Fat is a terrific energy source (when your body burns 1g of fat, it gets 9 calories of energy; in contrast, when you burn 1g of carbohydrate or protein, you get less than half that – only 4 calories of energy). 
Fat is also a key component of cell membranes throughout the body and, if you eat the right type of fat, the nutrient can reduce internal inflammation. Eating fats ensures delivery of essential fatty acids to your body (like omega-3 and omega-6 fatty acids*). Fats also help with the digestion and absorption of fat-soluble vitamins (vitamins that require fat in order to be absorbed from food and transported throughout the body). Examples of these include vitamins A, D, E, and K.
Fats have, traditionally, been divided into two categories: saturated and unsaturated (or “bad” and “good”). Unsaturated fats are liquid at room temperature (think oil), while saturated fats are solid at room temperature (think butter). But I’m going to break them down a little further for you, into four categories: monounsaturated fats, polyunsaturated fats, saturated fats, and trans fats.
Monounsaturated fats (or MUFAs as they are affectionately termed) are mostly found in plant-based food sources. Examples of these include olive oil, canola oil, peanut oil, avocados, pecans, and peanuts. These are excellent for you to cook with or to throw on top of your salad for some flavor.
Polyunsaturated fats (or PUFAs) are mostly plant- and fish-derived, including sunflower oil, sesame oil, soybean oil, flaxseeds, sunflower seeds, soybeans, tuna, salmon, walnuts, and most other nuts. PUFAs are usually a fantastic source of Omega-3 fatty acids (fish and flaxseeds are great examples) which are severely lacking in the average American diet.
Saturated fats, by contrast, are solid at room temperature. Basically any animal product will contain saturated fat – examples include beef, lamb, pork, bacon, cheese, full-fat yogurt, butter, whole milk, etc. Snack foods and bakery items that use tropical oils (like coconut, palm, and palm kernel oils) also contain saturated fats, which add to the taste and shelf-life of processed foods (after trans fats were forcibly removed, food manufacturers added saturated fats back in). Saturated fats are linked with heart disease because they have been found to raise harmful cholesterol levels (LDL, or the “bad” cholesterol).
How Bad Could They Be?
Studies have found that eating just one meal rich in saturated fats (say, a cheeseburger and fries from McDonald’s) is enough to raise blood cholesterol levels and damage arteries – just one meal!
In general, aim to keep your saturated fat to less than 20g per day. What does this look like? To give you an idea, one small (3oz) piece of filet mignon has about 10g saturated fat. If you already have risk factors for heart disease, such as high cholesterol, high blood pressure or a family history of heart disease, and if you’re a man over 45 or a woman over 55, then the American Heart Association recommends no more than 7g saturated fat per day. It is definitely a challenge to avoid saturated fats in today’s society, but the key to success is in choosing low-fat dairy products, eating red meat in moderation, and really paying attention to those nutrition labels on packaged foods.
Trans fats, the fourth category, are another type of saturated fat or, more accurately stated, an artificially-saturated fat. I’ve devoted an entire post to trans fat, but I’ll review the details again here as well. Trans fats are usually found in processed baked goods. Not only do trans fats raise LDL cholesterol like regular saturated fats, they lower “good” cholesterol levels (HDL) as well. Studies have proven that the incidence of heart disease increases exponentially with the amount of trans fat you consume in your lifetime, and preliminary studies have shown trans fats to raise insulin resistance, increase fat around the abdomen (which is also a risk factor for heart disease), and promote internal inflammation. You can tell a food item contains trans fat if its ingredient list reads “hydrogenated or partially hydrogenated vegetable oil”. If you focus on eating whole, natural foods like vegetable oils, fish, whole grains, and fresh produce, then you’ll naturally be eating trans fat free.
The take-home lesson: You should be aiming for a balanced diet rich in monounsaturated and polyunsaturated fats. These foods include olive oil, vegetable oils, avocados, seeds, nuts, and fish. Ensuring your fats are unsaturated will give you the greatest health benefits, while still allowing your meals to be tasty and flavorful. Eat foods containing saturated fat in moderation, especially if you have a family history of heart disease. And lastly, avoid trans fats altogether. Be especially aware of the restaurants you frequent – ask if they’ve eliminated trans fats from their kitchens or research it for yourself online. As an educated consumer you have the power to control your health and the health of your family. Just remember: Not all fats are bad!
*Your body can’t produce these fatty acids and needs a steady supply in your diet in order to get them.
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