It’s become common practice to classify fat into two categories—“good” and “bad”—to make it easier to identify which ones you should include more of in your diet and which ones to reduce or avoid. Certainly when we talk about fighting aging, we want to optimize the benefits of good fats and minimize the damage from the bad ones.
First you should understand that “fat” comes in four main types: saturated, polyunsaturated (which includes omega-3 and omega-6), monounsaturated, and trans fats. Fat is essential for life: most of the body’s organs—especially the brain—could not function without it. But “essential” does not mean you need large amounts of it. Although the Dietary Guidelines recommend Americans consume 20 to 35 percent of their calories from fat, the lower end of that range is much healthier and realistic given that the majority of people in the United States are overweight or obese and that diseases associated with high-fat intake (e.g., heart disease, stroke, some cancers) are responsible for the majority of disease-related deaths.
“Good fats” include monounsaturated fats and omega−3 fatty acids, a type of polyunsaturated fat. These fats typically are not listed on nutrition labels and so information about their values in foods is usually not readily available. You can calculate the amount of good fat in a product by subtracting the sum of bad fats from the total fat value. The resulting number is a fairly accurate idea of the amount of good fat in the product, although the figure may also represent some of the polyunsaturated fat called omega-6, which is sometimes good, sometimes bad. In the nutrition counter in this book, we provide values for total fat, bad fats, and good fats.
Although fats can have many negative effects on your health and contribute to aging, they also have many anti-aging benefits if you eat the right ones. That’s why it’s important to eat a balanced amount of good and bad fats. What does that mean? Your intake of bad fats should be less than 10 percent of your total caloric intake, and your intake of good fats should be at least 15 percent to 20 percent of your total caloric intake. Based on a 2,000 calorie per day diet, less than 200 calories should come from bad fats, and 300 to 400 should come from good fats. You should remember that all fats provide 9 calories per gram, which is more than twice as much as the calories supplied by carbohydrates and protein (4 per gram). So if you order a fast-food fish sandwich that has 15 grams of saturated fat and 2 grams of trans fat, you’ve nearly reached your daily limit for bad fats with one food item alone (9×17 = 153 g).
So what are some of the benefits of eating a balanced amount of good and bad fats?
They help the body absorb the fat-soluble vitamins (A, D, E, and K). This ability declines with aging.
They make you feel fuller, which helps you resist the temptation to eat between meals and before bed.
They help keep the brain healthy. The brain is composed of 60 percent fat, and if you deprive your body of a sufficient amount of good dietary fats, symptoms associated with aging, such as poor concentration, faulty memory, and reduced acuity, are likely to occur and with greater severity.
They help keep the immune system operating optimally so it can fight off infection, promote wound healing, and reduce the risk of cancer.
Age-related changes to skin, hair, and nails can be reduced.
Fats help the gastrointestinal system avoid constipation, bloating, and other digestive problems that are common as we age.
A small amount of saturated fat is needed by the liver to manufacture cholesterol, which the body uses to produce hormones. Restoration of declining hormone levels, which occurs with age, is an important factor in the fight against aging (see “Balancing Hormones”).
Fats help maintain a healthy nervous system.
Good sources of monounsaturated fats and omega-3 fatty acids include olive oil, avocadoes, salmon, walnuts, herring, and olives.
Bad fats include saturated fat, which is most often found in animal products, including meats, poultry, fish, and dairy products, as well as some tropical oils, such as palm and coconut; and trans fat, an artificial fat created when an unsaturated fat is bombarded with hydrogen atoms, resulting in a partially saturated fat.
Bad fats contribute to aging in a big way, namely:
Saturated fats increase the amount of “bad” cholesterol (low-density lipoprotein, LDL) in the bloodstream, which causes heart disease, atherosclerosis, and restricted blood flow.
Saturated fats are associated with insulin resistance, a leading cause of diabetes.
Both saturated fat and trans fat are associated with an increased risk of colon cancer.
Eating trans fat doubles the risk of heart attack by increasing the levels of LDL cholesterol, decreasing the levels of HDL (high-density lipoprotein) cholesterol (the “good” cholesterol), and promoting the formation of blood clots, all of which increase the risk of heart attack and stroke.
Trans fat increases triglyceride levels, which increases the risk of developing blood clots.
Trans fat causes inflammation of blood vessels by increasing levels of C-reactive protein, which in turn increases the risk of heart disease.
Liver function, the immune system, and reproductive function are all harmed by the consumption of trans fat.
What You Can Do Now
A diet high in saturated and trans fat is associated with elevated blood cholesterol levels, which can result in heart disease and other serious medical conditions. The nutrition counter in this book can help you identify the amount of bad fats in foods so you can make healthier choices. You can also reduce the amount of bad fats in your diet if you:
eat more fruits, vegetables, and whole grains.
choose non-fat and low-fat dairy products.
remove the skin from poultry.
steam and sauté foods rather than fry them.
limit meat consumption to lean cuts while avoiding organ meats.
regularly substitute plant protein for animal protein (e.g., beans, peas, lentils, tofu, tempeh).
read ingredient labels and avoid foods that contain trans fats, which appear as “partially hydrogenated vegetable oil,” “hydrogenated oil,” or “margarine.” Baked goods, crackers and cookies, processed and frozen dinners, fried foods, and margarines typically contain trans fats.