Is Fat Getting A Bad Rap?Kate Murphy
Phobic about fat? With all the low-fat, reduced-fat, and fat-free food products crowding grocery store shelves, it's hard not to fret about it. True, fat is high in calories, and excessive consumption has been linked to heart disease and cancer. But fat could be getting a worse rap than it deserves. "When communism collapsed, fat took its place" as the root of all evil, and "it isn't true," says Walter Willett, chairman of the nutrition department at the Harvard University School of Public Health. In fact, consuming some fat is necessary to good health, although experts disagree about how much and what kinds of fat are most beneficial.
Despite the fear it promulgates in many a diehard dieter, fat is as vital a nutrient as proteins and carbohydrates. It's necessary for the absorption of fat-soluble vitamins (A, D, E, and K), cell construction, nerve function, and digestion, and it is the precursor to hormones that regulate everything from metabolism to circulation. Furthermore, fat is the body's most concentrated source of energy, delivering 9 calories per gram, compared with the 4 calories per gram provided by proteins or carbohydrates. And without fat's pliable cushion, the body has no insulation from cold or shock absorption to protect bones and vital organs.
"Serious health implications arise when people don't eat enough fat," says Artemis Simopoulos, director of the Center for Genetics, Nutrition & Health, a nonprofit educational organization in Washington. Some early warning signs of fat deficiency are dry skin, brittle hair and nails, chronic constipation and other forms of gastrointestinal distress, menstrual abnormalities, fatigue, anemia, impaired wound healing, soreness of the joints, headaches, and memory loss.
Don't hoist a cheeseburger to your health, though--there are a boatload of caveats. First, it's important to know that several types of fat exist and that they differ in the way they affect the body. Saturated fats are solid at room temperature and derive mainly from meat and dairy products. Eating too much saturated fat can raise LDL or "bad" cholesterol levels in the blood, which increases the risk of heart attack and stroke. Additionally, some studies have linked diets high in saturated fat to cancers of the colon, rectum, endometrium, and breast. But the research is sketchy, since high-fat diets also tend to be low in fruits and vegetables, which contain the fiber, vitamins, and phytochemicals that may protect against cancer.
BUILDING BLOCKS. Unsaturated fats are liquid at room temperature and, depending on their chemical structure, are classified as monounsaturated (examples are canola and olive oil) or polyunsaturated (including safflower, corn, peanut, and fish oil). Neither type raises blood cholesterol levels. Indeed, research suggests they actually lower cholesterol counts. However, polyunsaturates have been found to lower the "good" HDL cholesterol, which seems to prevent heart disease, along with the "bad," artery-clogging LDL. Monounsaturates lower LDLs while leaving HDLs alone. So, monounsaturates rule, right? Not really. Only polyunsaturates contain the essential omega 3 and omega 6 fatty acids necessary for proper nerve and vascular function.
To further complicate matters, "trans-fatty acids" must be considered. Fatty acids are the building blocks of all fats. Trans-fatty acids have been subjected to a process called hydrogenation, whereby food manufacturers solidify unsaturated vegetable oils through the application of extreme heat. The resultant hydrogenated or partially hydrogenated oil (found in margarine, fried fast foods, and most commercially available cookies, crackers, breads, frostings, pies, and pastries) has a creamy texture and is less likely to spoil, but researchers have found that like saturated fats, trans-fatty acids raise LDL cholesterol. Worse, hydrogenated oils also lower HDL-cholesterol, to deliver a double whammy.
GREAT DEBATE. So, given that the body needs fat and there are all these different sources of fat, what kinds of fats are healthy to eat and in what quantities? "That's where you start having considerable debate," says Joseph Judd, research leader of the diet and human performance laboratory at the U.S. Agriculture Dept.'s Human Nutrition Research Center in Beltsville, Md. For example, Dean Ornish, director of the Preventive Medicine Research Institute in Sausalito, Calif., and author of several best-selling diet books, strongly advises against eating any fat other than what can be derived from whole vegetables and grains--a strategy he figures will provide 20 to 25 grams of fat, or 10% of total daily calories.
This contrasts with the recommendations of the USDA and American Heart Assn. for a 30% fat diet, with 10% coming from saturated sources and the remaining 20% from polyunsaturates and monounsaturates. Then there is Edward Siguel, a fatty-acids researcher in Boston, whose published findings indicate people need up to 30 grams of polyunsaturated fats every day. Beyond that, he says it doesn't matter how much or what kind of fat people eat, as long as "they get all the proper nutrients and don't gain weight."
Harvard's Willett says disagreements about fat intake exist because research has yet to prove absolutely a strong relationship between a type or amount of fat and wellness. Looking at the excellent health statistics of countries in Asia, where average fat consumption is around 15% (mostly polyunsaturated), and Scandinavia, where it is over 40% (equal parts saturated, monounsaturated, and polyunsaturated) of total daily calories, he says, "it's hard to find the link between fat in the diet and health."
Still, that's not license to gorge on grease. The better course is to avoid extremes. Most nutrition experts warn against diets that are overly restrictive or indulgent. "You'll get into trouble either way," says Judd of the USDA. Extremely high-fat diets add excessive pounds and cholesterol, whereas very low-fat diets not only deprive the body of an essential nutrient but also may overstimulate the metabolism to transform simple carbohydrates into fat. A 1995 study at Rockefeller University in New York compared 10%-fat and 40%-fat diets and found that the lower-fat diet raised the level of saturated fat in the blood. "Very low-fat diets are like turning people into cows," explains Scott Grundy, director of the Center for Human Nutrition at the University of Texas Southwest Medical Center in Dallas. "Cattle don't eat fat, but after a good while grazing in the pasture, their tissues are full of saturated fat."
BAD BEHAVIOR. So take a sensible approach to dieting: everything in moderation. Nothing should be off-limits, nor should it be open season on any single food. "Concentrate on the overall balance and quality of the diet rather than one particular facet, like fat," says Adam Drewnowski, director of the Human Nutrition Program at the University of Michigan in Ann Arbor. He emphasizes eating a variety of foods, including those with fat. "Your source of fat shouldn't be just hamburger or olive oil or safflower oil," he says. "You need them all."
Of course, saturated fat and trans-fatty acid intake should be limited, because of their connection to cholesterol. But "there's no reason to deprive yourself of anything entirely," Drewnowski says. Besides, abstinence from fat can lead to other destructive behaviors. Studies show that people who observe extremely strict diets are prone to binge eating and are more likely to abuse alcohol, drugs, and cigarettes. Finally, for those who are watching their weight--worry about calories, not fat. Too many calories from any source can tip the scale in the wrong direction. An active lifestyle, in which calories taken in match what's burned off, prevents the addition of unwanted pounds. That's the real skinny on fat.