Fat replacers have facilitated the development of reduced-fat and fat-free foods that have the taste and texture of high-fat foods, but with less fat and fewer calories. The food industry provided a variety of low-fat products, and a segment of the public responded by consuming them. Julie M Jones and Satya S Jonnalagadda, PhD, explore the options on the table
Obesity rates for both children and adults have increased dramatically in the US, the UK and Western Europe.1,2,3 The epidemic is fuelled by readily available, inexpensive food, especially energy-dense, high-fat foods and increased portion sizes, which both lead to the over-consumption of calories.4,5,6,7,8,9 Because increases in the energy density of foods have also been shown to increase energy intake, it is reasonable to assume that ingestion of foods that lower energy density by any means, including the use of fat replacers, would result in lower overall food energy intake.10,11,12 Thus, manipulation of the energy density of the diet can lower energy consumption by 20-25 per cent, and can lead to modest changes in body weight.13,14
These data indicate that a reduction in the proportion of fat in the diet by 10 per cent can result in a corresponding reduction of 238kcal/day of total energy intake, and can produce a weight loss of -3.2kg. Therefore, lowering the fat content of foods by using fat replacers has potential for lowering the energy density of foods, which can be helpful in the struggle to maintain a healthy weight.15
Fat replacers and their uses
Fat replacers are called by many synonyms with various nuances in their usage. (See sidebar, below.) Fat replacers in food must do two things if they are to help consumers with weight loss. First, they must replicate all or some of the functional properties of fat and, in so doing, impart the sensory properties attributed to fat such as a rich, creamy mouthfeel and a tender texture. No one fat replacer is likely to provide all the functions of fat, such as flavour, texture, lubrication, keeping quality, volume or heat transfer.
Second, they must lower the fat and calorie content of the food. They do this either by enabling the holding of air and water or by being less well absorbed. Fat replacers are most frequently used to replace fat in products with a high fat content, and are used in a variety of food products including frozen desserts, processed meats, cheese, sour cream, salad dressings, snack chips and baked goods. At the height of the interest in low-fat foods, more than 1,000 fat-modified foods were introduced, with fat-modified snacks being the fastest-growing category of products in supermarkets at the time.16,17
Categories of fat replacers
There are three broad categories of fat replacers on the market. Because fat replacers may contain calories, food manufacturers using they should ensure that the final products are not only reduced in fat, but also reduced in calories. In the end the food with fat replacers will be of little value for weight reduction if it fails to cause a significant reduction in calories.
Carbohydrate-based fat replacers: These use carbohydrate polymers and dietary fibres, such as cellulose, dextrins, maltodextrins, polydextrose, gums, fibre and modified starch, to replace fat. Carbohydrate-based fat replacers can provide up to 4kcal/g if the carbohydrate is fully digestible. Often the calories are even lower because the fat replacers are either dietary fibres, which are not digested or only fermented to some degree, or digestible carbohydrates mixed with water so they provide 0-2kcal/g. In some cases fibres, such as cellulose, are ground into microparticles that can form gels for use as fat substitutes, such as Oatrim and Z-trim.
Carbohydrate-based fat replacers are used in a variety of foods including dairy-type products, frozen desserts, sauces, salad dressings, processed meats, baked goods, spreads, chewing gums and sweets, but they cannot replace fats in frying.
Protein-based fat replacers: These are made from many different types of protein, but soy, egg, milk or whey proteins are common. Microparticulation of protein into tiny, spherical particles that provide a creamy mouthfeel similar to fats helps protein to function as a fat replacer. Blending protein with carbohydrates is another way to create fat replacers. Several studies have shown that combinations of ingredients in fat-replacer formulations create synergy that helps lower fat and helps retain desirable product texture.18,19,20,21,22
Fat replacers from protein and protein blends do provide 4kcal/g, but they may provide only 1-4kcal/g either because they hold water or are used in lesser amounts than fat. For example, 1g Simplesse can replace 3g of fat in cream.
Protein-based fat replacers have been used in fat-free ice cream; low-fat cheese; low-fat baked goods; and reduced-fat versions of butter, sour cream, cheese, yoghurt, salad dressings, margarine, mayonnaise, baked goods, coffee creamers, soups and sauces. Often a combination of these fat replacers can have tremendous potential in the development of fat-modified foods with greater acceptability while lowering the total energy and fat intake.
Fat-based fat replacers: These include common fats that have had chemical alterations of fatty acids so that they deliver less than 0 calories per gram. Some fat-based fat replacers pass through the body partially or totally unabsorbed. Thus they provide less than 9kcal/g or no calories at all. For example, Olestra (Olean) is a sucrose polyester consisting of a mixture of hexa, hepta and octa esters of sucrose, esterified with long-chain fatty acids. Other fat-based fat replacers, such as Salatrim (short- and long-chain triglyceride molecules) and Caprenin, a substitute for cocoa butter in candy bars, are only partially digested and absorbed, and provide 5kcal/g. Some fat replacers, such as Enova oil, are structured diglycerides and are metabolized differently from triglycerides so that some of the energy is lost as heat rather than stored as adipose.
Emulsifiers can be another type of fat-based substances that can be used as fat replacers. They may be used with water to replace all or part of the shortening content in cake mixes, cookies, icings and vegetable and dairy products. They provide the same number of calories as fat, but because less is used in the formulation, the resultant product has less total fat and energy. Mono- and diglycerides are currently used in foods as fat replacers and other substances such as dialkyl dihexadecylmalonate, esterified propoxylated glycerol and trialoxytriartallate are in various stages of development.
Fat replacers and weight loss
Fat replacers can potentially impact overall diet quality and help with weight loss and maintenance. For example, salad dressings and spreads made with fat replacers can help enhance appeal of other nutritious foods such as vegetables and fruit. Thus, fat replacers may help increase the intake of satiety-producing, low-calorie, high-fibre, nutrient-dense foods, while adding few calories. In meat and other food items, fat replacers such as prunes, raisins, cherry paste or wild rice replace some of the fat and increase the antioxidant value of foods while lowering calories. Impact of protein-based: Because these are from milk powder, whey, soy or legumes, they not only have potential to lower calories, but also can increase the protein in the diet or offer some nutritional advantages of the individual protein. Some preliminary data indicate the protein may have an impact on satiety and food consumption in the short term.23,24 Furthermore, protein-based fat replacers have the potential to increase the protein in the diet, and a high protein-to-carbohydrate ratio has been associated in studies with greater weight loss than diets with a lower ratio.25 Dairy-based proteins may add calcium, which has been shown in some studies to be related to weight loss.26 Thus protein-based fat replacers might offer two benefits to the calorie-conscious eater.
Impact of fibre-based: These may offer calorie savings while increasing fibre in the diet.27 Some types of fibre have been shown to regulate food intake, and to aid in both preventing weight gain and helping with weight maintenance.28,29,30,31
One study with male diabetics shows the utility of a fibre-based fat replacer in dealing with obesity and complications associated with it. In this study, those who chose diets rich in fibre-based fat replacers along with sugar replacers and other lifestyle changes reduced body weight and body mass index more than those eating the standard treatment plan. In addition, there were greater decreases in HbA1C (the best measure of glucose because it will be high only if glucose has been elevated for a sustained period of time), and increases in HDL cholesterol.32
In like manner, inclusion of foods made with fat replacers such as Mimex or Oatrim (a powdered soluble oat fibre containing beta-glucans) has been observed to not only lower blood lipid and systolic blood pressure, and improve glucose tolerance and antioxidant status, but it also lowers body weight.33,34,35 Researchers noted that those in the Harvard Nurses' Health Study cohort who had the highest fibre intakes were least likely to gain weight.
Impact of fat-based: These have also been associated with caloric dilution,36 decreased caloric intake and changes in appetite.37 In a study with otherwise healthy and overweight subjects eating foods prepared with fat emulsion of palm oil and oat oil (Olibra, now branded Fabuless by DSM) as a fat replacer, there was decreased total energy intake for up to 36 hours post-consumption. Use of Olibra as a fat substitute in yoghurt significantly reduced the energy and macronutrient intakes relative to use of milk fat.38,39,40
Impact of fat replacers: Use of fat replacers in foods such as mayonnaise, hot dogs and chips has been shown to decrease the energy and fat in products by as much as 50 per cent. In a study where subjects were offered either full-fat or fat-free Olestra-containing chips, total fat intake was reduced from 32-43 per cent in regular chips to 27-30 per cent with Olestra chips.41
Researchers noted that providing free access to reduced-fat products resulted in a reduction in energy intake and percentage energy from fat, while it was associated with an increase in percentage energy from carbohydrate, especially among individuals classified as high-fat consumers.42 Body weight remained stable in the reduced-fat group while it increased significantly by about 1kg in the full-fat group. In addition, cardiovascular disease risk factors such as blood lipids, and hemostatic factors were lower in the reduced-fat group compared to the full-fat group.
In other studies, researchers showed that the selection of low-fat grain mixtures, cakes, cookies and pies not only lowered fat and saturated fat, but resulted in a less energy-dense diet.43,44 The individuals consuming lower-fat foods were more likely to meet nutrient requirements than those consuming higher-fat foods even though they were eating 400-500kcal less.44
Thus, one strategy for combating the obesity epidemic may involve the switch from consumption of full-fat products to lower-calorie, reduced-fat alternatives. An estimated 30 per cent reduction in fat calories and a total calorie reduction of 800kcal can be achieved per week if fat-free products from food categories such as cheese, sour cream, frozen desserts, commercial sweets and baked goods were substituted for their regular versions.45
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On the other hand, foods prepared with fat replacers that neither lower calories nor encourage the consumption of foods that are central to the dietary recommendations may do little to improve the quality of the diet. Excessive consumption of brownies, cookies, snack cakes and chips and other such foods made with fat replacers may do little to help in the battle against obesity. This may be especially problematic if the consumer erroneously believes that fat free means calorie free and takes this as a license to consume unlimited amounts.
Julie M Jones is professor in the department of nutrition and food science at College of St Catherine, Minnesota. Satya S Jonnalagadda, PhD, is senior medical affairs specialist at Novartis Medical Nutrition, Minnesota. Respond: [email protected]
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