"More than 90 percent of the U.S. adult population reports consuming low- or reduced-fat foods and beverages, many of which contain fat substitutes, yet the number of overweight individuals continues to increase," says Judith Wylie-Rosett, Ed.D., R.D., a member of the American Heart Association's Nutrition Committee and author of the statement.
Fat substitutes are compounds incorporated into foods to provide them with the same qualities of fat, such as moisture retention and texture.
"The bottom line is that foods made with fat substitutes, used in moderation, may provide some flexibility in food selection, but are not an effective strategy on their own for weight control. Often, reduced-fat versions of products have the same or even more calories than their full-fat versions," says Wylie-Rosett, a professor of epidemiology and social medicine at the Albert Einstein College of Medicine in the Bronx, New York.
The statement aims to clarify the role of the fat substitutes used in many food products and provides information on the pros and cons of including them in the diet.
The fat substitutes seem to have led to an overall trend for less fat in the diet. Americans have nearly met the government's population-wide goal of reducing fat consumption to no more than 30 percent of total calories. A 1988-1991 government survey showed that Americans consumed about 34 percent of total calories from fat, compared to 40 to 42 percent of total calories in the 1950s.
"We've done well in getting out the message about reducing fat intake," says Wylie-Rosett. "Now we must put the emphasis on obesity, which has doubled in the last 20 years. During the 1990s the number of people in the United States with diagnosed diabetes increased by about 33 percent. Almost all of this increase is related to the rise in obesity.
"Americans are confused about reduced fat products in general – for example, there is a common misperception that if you consume lower-fat versions of products you don't have to worry about portion size or total calories," she says. "Eating smaller portions of food and increasing physical activity are still the most effective ways to lose weight and maintain a healthy weight."
The problem is that the plethora of 'fat-free' products has led to consuming more sweet rolls, cookies and frozen yogurt. "These foods should be consumed in moderation. There is nothing wrong with enjoying a reduced-fat confection, but it should be a treat, rather than a major source of calories in your daily menu," says Wylie-Rosett. "A healthy diet, like the one recommended by the American Heart Association, doesn't just limit fat, but also emphasizes foods such as fruits, vegetables, whole grains and other foods that have positive benefits for your health, such as dietary fiber, vitamins and minerals."
Thirteen kinds of fat substitutes were examined – six derived from carbohydrate, two from protein and five from fat. Those formulated from carbohydrates such as polydextrose and gums, or protein such as modified whey (used in low-fat baked goods and dairy products) have little or no effect on digestion, absorption or metabolism of vitamins and minerals. Some fat-based substitutes, such as caprenin and salatrim, used in baked goods and dairy products, also appear to have no deleterious effect on metabolism. Absorption is the movement of food from the intestines to the circulatory system.
The statement raises concern about olestra, a fat-derived fat substitute used in savory snack foods, such as potato chips. Olestra reduces the absorption of fat-soluble nutrients, such as carotenoids, and the fat-soluble vitamins A, D, E and K. Vitamins A and E are anti-oxidants, which research has linked to a decrease in coronary heart disease. The body uses Vitamin K in the blood clotting process. Vitamin D is needed for normal calcium absorption and metabolism.
To compensate for this, the manufacturer must add these vitamins into olestra-containing foods. Little is known about potential interactions between olestra and medications and ingredients in food products that can affect fat-soluble nutrient movement and absorption rates in the gastrointestinal tract. Olestra has also been shown to affect stool composition – 40 grams of olestra can result in a misdiagnosis of malabsorption, in which nutrients are excreted unchanged into the stool, rather than being used by the body.
"Don't 'binge' on a giant bag of chips containing olestra," says Wylie-Rosett. "If you choose to eat snacks containing olestra, limit your portion to one ounce and check the number of servings per bag. This is a relatively new fat-replacer, and the jury is still out on the long-term health effects."
The association's dietary guidelines for healthy individuals still recommend limiting total fat to less than 30 percent of total calories, with only 10 percent (7 percent for those with known cardiovascular disease) coming from saturated-fat and trans-fat combined. Saturated-fat and trans-fat are the main culprits in raising blood cholesterol, a risk factor for cardiovascular disease. Saturated fat is found in products derived from animals, such as meat, milk, butter and also in some tropical oils, such as palm kernel, palm and coconut oil. Trans-fat is also known as hydrogenated fat, and is found in many commercially baked goods, such as crackers, cookies and stick margarines. At present, trans-fat content is not part of the FDA's label requirement.
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