Fat substitute is a substance used in foods in place of fats and oils. Fats are a solid type, and oils, a liquid type, of lipids, a class of substances found in all living things. Lipids are essential for proper growth and development and for good health. However, consuming fats and oils at more than about one-third of calories in a diet can lead to undesirable weight gain. It can also increase risk of certain kinds of cancer and of diseases of the heart and arteries. Fat substitutes are used to help reduce the amount of fats and oils people consume in foods.
Some fat substitutes are based on modified lipids. Fats consist mainly of triglycerides, compounds made up of one molecule of an alcohol called glycerol combined with three molecules of fatty acids. Each of these fatty acids is a long chain of carbon atoms with hydrogen atoms attached to them. Lipids called medium chain triglycerides are formed using shorter fatty acid chains. These lipids, which are liquid, are used primarily in sports drinks and nutritionally enriched beverages. Another type of lower-calorie lipid combines short and long fatty acid chains to produce solid or semisolid substitutes called structured lipids. Fat substitutes of this type are used primarily in baked goods and chocolate.
Another type of modified lipid is made by attaching long fatty acid chains to other molecules, usually sucrose (sugar). Such fat substitutes add no calories because they cannot be digested, but they also reduce the body’s absorption of several fat-soluble vitamins. These substitutes can withstand heat, and so can be used to fry foods. The Food and Drug Administration of the United States approved a fat substitute of this type, called olestra, in 1996 for limited use in fried snack foods.
Other fat substitutes are based on carbohydrates or proteins, two other classes of substances found in living things. Most fat substitutes are unmodified starches, which are types of carbohydrates, and proteins. Fat substitutes may also be made from modified proteins and carbohydrates. Proteins and carbohydrates are polymers, molecules made up of hundreds, often thousands, of smaller molecules arranged in long chains. Water molecules can bond along these chains to form gels that mimic the consistency and smoothness of lipids in foods. Such fat substitutes include those made from egg and milk proteins or natural fruit bases that contain pectin, a material that forms jellies. Most carbohydrate-based fat substitutes can be used in a variety of foods, including baked goods, salad dressings, cheese, and frozen desserts. Gels formed from proteins break down when heated. Such fat substitutes are used primarily in products that do not require heating, such as frozen desserts and peanut butter.
