Ask the Expert: Healthy Fats

The Experts: Dr. Walter Willett and Amy Myrdal Miller

We asked Dr. Walter Willett of Harvard School of Public Health and Amy Myrdal Miller, M.S., R.D. of The Culinary Institute of America to explain why it’s time to end the “low fat is best” myth—and to provide ideas for how to use healthy fats in the home kitchen.


1.Should I ditch a low-fat diet?

Walter Willett: If you’ve been able to keep your weight, blood cholesterol, and blood glucose under good control while eating a low-fat diet, this type of diet may be working for you. But for many people, low-fat diets don’t work. In fact, dozens of studies have found that low-fat diets are no better for health than moderate-or high-fat diets—and for many people, they may be worse.

Low-fat diets are usually high in carbohydrates, often from rapidly-digested foods such as white flour, white rice, potatoes, sugary drinks, and refined snacks. Eating lots of these “fast carbs” can cause quick, sharp spikes in blood sugar and insulin levels, and over time can increase the risk of diabetes and heart disease. High-carbohydrate, low-fat diets also have a negative effect on the fats and cholesterol in our blood: They raise “bad” blood fats (triglycerides) and they lower the “good” blood cholesterol (HDL), both of which can increase the risk of heart disease. These diets also tend to increase blood pressure.

For many people, low-fat diets are not satisfying. People finish a meal and within a few hours, they are hungry again, seeking more low-fat fixes for their hunger. This vicious cycle leads to weight gain and, in turn, to the conditions associated with excess weight (such as blood triglycerides, low HDL cholesterol, high blood pressure, and diabetes).

2. Are “fat free” foods healthy?

Amy Myrdal Miller: Some foods in their natural state contain little or no fat—for example, most fruits, vegetables, whole grains, dried beans. And of course these are healthy choices. But processed foods billed as “low fat” and “fat free” are often higher in salt, sugar, or starch than their full-fat counterparts, to make up for the flavor and texture that’s lost when food manufacturers slash fat. So they are not necessarily “healthy” choices. For example, low-fat and non-fat salad dressings are nearly always higher in sugar and salt.

3. Will eating fat make me get fat?

Willett: No, it’s a myth that eating specifically high-fat foods makes you fat. Eating or drinking more calories than you need from any source, whether it’s fat, carbohydrate, protein, or alcohol can lead to weight gain. Over the past 30 years in the U.S., the percentage of calories from fat has actually gone down, but obesity rates have skyrocketed. Sugary soft drinks don’t contain any fat—yet the billions of gallons of sugary beverages that Americans drink each year have been a major contributor to the obesity epidemic.

4. Can I lose weight on a low-fat diet?

Willett: It’s possible to lose weight on any diet. But carefully-conducted clinical trials find that following a low-fat diet doesn’t make it any easier to lose weight or keep it off. In fact, study volunteers who follow moderate- or high-fat diets lose just as much weight, and in some studies a bit more, as those who follow low-fat diets.

Calories are what count for weight loss, so it’s important to find a lower-calorie eating plan that you can follow—and a lower-calorie plan that’s good for lifelong health. Low-fat diets raise triglycerides and lower good cholesterol, so for many folks, they’re simply not the best choice for health. For some people, high intake of carbohydrates, particularly if they come from refined rather than whole grains, can make weight control more difficult.

5. Are all kinds of fat equally healthy?

Willett: Some types of fats are healthier than others. Unsaturated fat is the healthiest type of fat. Plant oils, such as olive, canola, corn, peanut and other nut oils; nuts, such as almonds, peanuts, walnuts, and pistachios; avocados; and fish, especially oily fish such as salmon and canned tuna, are excellent sources of unsaturated fat. Eating unsaturated fat in place of refined grains and sugar can improve blood cholesterol profiles and lower triglycerides, and in turn, lower the risk of heart disease.

It is essential to include a special kind of unsaturated fat, called omega-3 fats, in the diet; good sources include fish, walnuts, flax seeds, and canola oil. Keep in mind that omega-3 fats from marine sources, such as fish and shellfish, have much more powerful health benefits than omega-3 fats from plant sources, like walnuts and flax seeds. But omega-3 fats from plant sources still are a good choice, especially for people who don’t eat fish.

Saturated fat is less healthy, since it raises “bad” cholesterol in the blood. We can’t completely eliminate saturated fat from our diets, though, because foods that are rich in healthy fats also contain a little bit of saturated fat. The best strategy is to limit foods that are very high in saturated fat, such as butter, cheese, and red meat, and replace them with foods that are high in healthy fats, such as plant oils, nuts, and fish. An alternative approach is to just use a very small amount of full-fat cheese, butter, cream, or red meat in dishes that emphasize plant foods such as vegetables, whole grains, and legumes.

Whatever you do, don’t replace foods that are high in saturated fat  with “fast carbs”—foods like white bread, white rice, potatoes, sugary drinks, and refined snacks—since eating too many of these fast carbs is just as bad for your heart as eating too much saturated fat.

Trans fat from partially hydrogenated oil (oil that has been chemically processed to make it more shelf-stable) is especially bad for health. Eating just a small amount of trans fat on a regular basis raises the risk of heart disease. So it’s best to avoid trans fat altogether. Most of the trans fat in people’s diets comes from commercially prepared baked goods, margarines, snack foods, and processed foods.  Many food makers are cutting trans fats from their products and replacing them with healthier fats. Still, you’ll need to scan Nutrition Facts labels to make sure that the food you eat is free of trans fats.

Keep in mind that most foods contain a mix of fats. The key to a healthy diet is to choose foods that are higher in unsaturated fat than saturated fat—and that do not contain any trans fat. When you cut foods like red meat and butter out of your diet, replace them with healthy plant oils, nuts, fish, vegetables, or whole grains—don’t replace them with white bread, white rice, potatoes, or other refined carbohydrates.

6. How can I cut back on trans fats?

Willett: Many food manufacturers are already removing trans fats from their products and replacing them with healthy fats. Similarly, many restaurants are removing trans fat from their menu items, so this is a big help. But you still need to pay attention to nutrition labels, to make sure that the food you buy does not contain any trans fats. Labeling laws allow food makers to say that a product has “0 grams trans fat” even if it contains up to 0.5 grams of trans fat per serving from partially hydrogenated oils. This may not sound like a lot of trans fat. But if you eat several servings a day of these foods, your trans fat intake can really add up. So to make sure that a food you are buying is truly trans fat free, check the Nutrition Facts Panel to make sure it has 0 grams of trans fat—and check the ingredients list to make sure it does not contain any partially hydrogenated oil.

 7. Are coconut oil and palm oil healthy?

Willett: Coconut oil and palm oil are higher in saturated fat than other plant oils. They are less harmful than partially hydrogenated oil, which is high in trans fats. But they are less beneficial for the heart than plant oils that are rich in unsaturated fats — olive, canola, sunflower, and other oils. Coconut oil increases good cholesterol, which may make it a good choice when cooking a dish that needs a little hard fat.

Read more about coconut oil and health.

 8. Is it okay to eat high-fat fried foods?

Willett: It’s okay to eat fried foods, as long they are prepared with frying oil that doesn’t have any trans fats. It’s also important to look at the types of foods being fried. In America, we eat lots of fried potatoes, which contain rapidly-digested starch, and it’s good to find an alternative. Fried foods are high in calories, and it is important to think about calories, because most of us need to keep our calories in check to avoid gaining weight. But that doesn’t mean you have to cut out fried foods—just choose smaller portions.

Myrdal Miller: Sweet potatoes are a great alternative for frying. Or you could just try making a smaller portion of fried potatoes, or pairing fried potatoes with other vegetables. If you’re in a restaurant and watching your calories, try sharing a fried dish with a friend. Or you could try ordering a half-sized portion of fried food along with a small salad.

9. Do I need to watch my percentage of calories from fat?

Willett: No. When you cook or read nutrition labels, don’t fixate on fat percentages. As long as you use healthy fats, and your keep your portion sizes modest, it doesn’t matter if your dish or meal has 30 percent, 40 percent, or more of its calories from fat. The same is true for your overall diet: Don’t worry about the percentage of calories from fat. Focus on choosing foods with healthy fats.

10. What’s better than a low-fat diet?

Willett: Try following a healthy fat, healthy carb diet, using two nutrition tools from Harvard School of Public Health as your guide: The Healthy Eating Plate and the Healthy Eating Pyramid. The Healthy Eating Plate offers a simple blueprint for a healthy meal: Fill half of your plate with vegetables and fruits, save a quarter of the plate for whole grains, and the rest for a healthy source of protein; the glass bottle to the left of the plate is your reminder to use healthy plant oils in cooking, on salads, and at the table. Think of the Healthy Eating Pyramid as your grocery shopping list: vegetables, fruits, whole grains, and plant oils are in the base, and healthy proteins—nuts, beans, fish, and chicken—are in the next tier, meaning that these foods should make it into your grocery cart every week. Refined carbohydrates and sugary drinks, as well as red meat and butter, are in the “use-sparingly” tip—so skip the soda and snack food aisle, the deli counter, and the steaks and chops at the butcher counter. You can download copies of the Healthy Eating Plate and Healthy Eating Pyramid from The Nutrition Source website.

11. Can you share any tips for cooking with healthy fats?

Myrdal Miller: Here’s a few ideas for how to use healthy fats in your kitchen:

  • Cook with healthy oils. Olive, canola, soy, peanut, sunflower, corn, and other oils from plants are the best choices, since they are high in healthy unsaturated fat. If you have a dish that requires the flavor of butter, use a very small amount of butter mixed with a neutral-flavored oil, such as canola oil. And keep in mind that it’s okay to cook with extra-virgin olive oil. The healthy fats in extra-virgin olive oil are stable at temperatures used in home cooking, with the exception of deep-fat frying or stir frying. Then we’d advise using an oil that’s more stable, like peanut oil.
  • Bake with healthy oils. You can replace the butter in many baked goods with vegetable oils. Just cut back on the amount of oi by 25 percent; butter contains some water, so that’s why you can use less oil. Pastry chefs at The Culinary Institute of America have done experiments making pound cake with canola oil instead of butter, and consumers prefer the taste and texture of the pound cake made with canola oil! Check out The Great Muffin Makeover for five new muffin recipes that use healthy oils and whole grains.
  • Serve healthy fats at the table. Drizzle extra virgin olive oil or nut oils on vegetables, instead of butter. Use peanut butter, trans fat-free margarine, or refrigerated extra virgin olive oil as a spread for whole grain toast, instead of spreading on cream cheese. With Mexican cuisine, serve guacamole as a topping instead of sour cream.
  • Pare calories by pairing healthy fats with low-calorie foods. Use oils and nuts to add flavor to lower-calorie, high-fiber foods, such as vegetables, beans, and whole grains. That way, it will be easier for you to stay within your daily calorie budget.
  • Cut “fast carbs” and replace them with “slow carbs” and healthy fats. “Slow carbs” include beans, non-starchy vegetables, and minimally-processed whole grains, such as whole wheat berries, barley, quinoa, or brown rice. There are many delicious ways to switch from fast carbs to slow carbs. For example, instead of making white pasta or potatoes as a side dish, try making smaller portions of whole grain pasta, quinoa, or dried beans, and prepare them with flavorful plant oils, nuts, and seeds. Try this recipe for whole wheat penne with pistachio pesto, or a quick hummus with pureed chickpeas and sesame paste (tahini). Instead of serving potato chips with soup or a sandwich, how about serving a side salad or crunchy raw vegetables with an olive oil-based dressing, like this oregano garlic vinaigrette?
  • Use full-fat cheese in small amounts. Low-fat cheeses are not really that much lower in saturated fat than their full-fat counterparts—and they are often higher in sodium. A healthier strategy is to just use a small amount of full-fat, full flavored cheese in a dish. And if you choose aged cheeses, you can use even less cheese—thanks to the aging process the fermentation products intensify, so a little offers lots of flavor.
  • If you’re serving chicken, there’s no need to strip the skin. Chicken skin has had a bad rap for being high in fat. But most of the fat in chicken skin is healthy, unsaturated fat—and cooking with the skin keeps the chicken flavorful and moist, so you don’t need to add as much salt or use a breaded coating.
  • Trade fish, nuts or tofu for beef and pork. At your next cookout, try serving salmon or turkey burgers instead of hamburger, shrimp kabobs instead of steak tips, tuna steak instead of rib eye. Be sure to brush fish and shellfish with a healthy vegetable oil to keep them from getting too dry. Instead of using pork for protein in your stir fry, try peanuts and tofu, like in this recipe for spicy lemongrass tofu.

12. How can I convince my family to eat healthy fats?

Recipes for Health: Nut-Based Sauces

Try these Mediterranean-inspired sauce recipes with vegetables, chicken, or fish:

Spanish Romesco Sauce (Red Pepper and Almond Sauce)
Turkish Muhammara (Red Pepper and Walnut Sauce)
Greek Skordalia (Almond, Bread and Garlic Sauce)
Turkish Tarator (Walnut and Garlic Sauce)
Italian Pesto alla Trapanese (Almond, Parsley, Basil, and Tomato Sauce)

Myrdal Miller: Introduce your family to the range of healthy foods and flavors from around the world that rely on healthy fat to deliver their great flavor. Think about the nut-based sauces of the Mediterranean that make other healthful foods, such as vegetables and fish, more appealing and flavorful. Share this article with your family members, so that they understand that the type of fat matters more than the amount of fat, and that low-fat cooking isn’t necessarily better for health. Tell them that you will cook with healthy fats, such as olive and canola oil, and you will serve foods that naturally contain healthy fats, such as avocados, nuts and fish. Promise to limit foods that are high in saturated fat—butter, cheese, red meat. And tell them that you’ll scan nutrition labels so that you can avoid foods with partially hydrogenated oil and keep your pantry and table trans-fat free.

Copyright © 2012 Harvard University and The Culinary Institute of America