Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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energy or fat consumption instead of the intended

decreases. Also, it is debated whether the overcon-

sumption of dietary fat in and of itself leads to nega-

tive health outcomes, or if it is the resulting increase

in overall energy intake due to the overconsumption

of dietary fat that contributes to adverse health out-

comes. Unfortunately, the message that much of the

general public has received is: ‘I can eat as much food

as I want as long as it is low in fat or fat-free.’

0004 This article summarizes the existing scientific

literature regarding the effects of adding low-fat/

fat-replaced foods to the diet on fat and energy

consumption, and discusses the efficacy of using

fat replacers as a means of reducing dietary fat

and total energy intake.

Background and Significance

0005 In the developed world and, recently in the develop-

ing world, high consumption of dietary fat has been

epidemiologically linked to a variety of medical con-

ditions, including obesity, coronary artery disease,

and certain types of cancer. Many regard it as the

top dietary problem in the USA. Currently, dietary

fat comprises nearly 34% of the energy content of the

American diet. Most health guidelines recommend

that no more than 30% of daily energy be derived

from dietary fat in order to reduce the incidence of

related morbidity and mortality.

0006 Perhaps the most obvious method of decreasing the

percentage of energy from fat is to substitute low-fat

foods for high-fat foods. However, it is difficult for

many people to restrict their food choices to achieve

this end. Laboratory-based experiments suggest that,

for most people, high-fat foods are overeaten because

they are highly palatable. When a substantial amount

of fat is removed from the diet, the resulting menu is

often bland and monotonous. Even those whose

health is directly threatened (postmyocardial infarc-

tion patients, those with type 2 diabetes or hyper-

tension) find it difficult to maintain long-term

compliance with a reduced-fat diet. The development

of fat-replaced foods has the potential to reduce fat and

energy consumption bysatisfying thepreference forthe

taste of a high-fat diet while consuming low-fat foods.

The recent availability of highly palatable reduced-fat

or fat-free foods offers consumers new choices, but

because there have been few controlled studies of how

these products will be used, questions remain about

their efficacy in reducing dietary fat intake.

0007 Several issues to consider when assessing products

made with fat replacers are:

0008 Why do many people eat more dietary fat than

the recommended 30% of total energy, and will

fat-replaced foods satisfy people’s desire to

consume high-fat foods?

0009Will consuming foods made with fat replacers aid

in lowering the intake of fat and energy, or will the

fat and/or energy reduction be compensated for in

subsequent episodes of eating?

0010Will these products be used in place of regularly

eaten foods, as a license to eat previously ‘forbid-

den foods,’ or to allow for increased consumption

of other foods?

Why is Fat Overconsumed?

Palatability

0011Fats contribute much of the texture, flavor, and odor

of a variety of foods. Although not usually consumed

in pure form, fat is readily consumed as part of com-

plex foods containing the other macronutrients (pro-

tein and carbohydrate) in varying amounts. Thus, it is

difficult to isolate a fat-specific preference in foods.

Fats contribute a number of sensory properties of

food. First is the olfactory perception of volatile

fat-soluble molecules that impart the characteristic

aroma to many foods. Second, fats endow foods with

certain textures (such as softness, oiliness, elasticity,

flakiness, viscosity, or smoothness) and mouth feel,

(the food’s distribution in the oral cavity during

chewing and swallowing). These textural and mouth-

feel characteristics enhance the richness of food flavor,

and positively influence the palatability of the diet.

0012A number of experiments have studied the nature

of diet palatability. Preferences for sweet/fat mixtures

such as milkshakes, cake frostings, and ice cream

have been identified by sensory panel testing. In one

sensory study, the palatability of sweetened, fat-free

milk and unsweetened heavy cream were both rated

relatively low, but the combination of sugar and fat in

sweetened heavy cream was highly appealing. Anec-

dotally, people who ‘crave’ sweet desserts often de-

scribe themselves as ‘carbohydrate cravers;’ however,

it is fat, not sugar, that provides the majority of the

energy in sweet, rich desserts. In addition, not just

sweetened, high-fat foods are considered highly pal-

atable. A survey of US military personnel found that

the most preferred foods were ‘savory’ high-fat foods

such as steak, French fries, and whole milk. Some of

the least preferred foods in this survey were vege-

tables, skim milk, and diet soda, which are very low

in fat. Other surveys of attitudes toward dietary fat

also indicate that highly preferred foods often have

a high-fat content. In these studies, taste is the

primary reason given for the selection of a particular

food. Because fat imparts the textural and mouth-feel

2248 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

characteristics associated with high palatability, high-

fat foods are often chosen.

Can Fat Preference be Changed?

0013 The question of whether our preference for high-fat

foods is innate or learned is of great importance. If it

is learned, it can presumably be more easily altered

than if it is innate. It is believed that the preference for

sweet taste, for example, is innate. A preference

for sweetness was useful in identifying foods that

were safe to eat, and may have aided survival for

our nomadic ancestors. It follows that an innate pref-

erence for fat may have also been adaptive for sur-

vival: consumption of a dense, easily stored energy

source would provide an energy reserve for periods of

scarcity. Unfortunately, if humans did acquire adap-

tations that favored high fat consumption, these

adaptations have become maladaptive in today’s so-

ciety, which is characterized by an abundance of fatty

food and opportunities to consume energy above our

metabolic needs.

0014 There is some evidence in favor of an innate fat

preference. Children generally display preferences for

high-fat foods. In experiments with high- and low-fat

yogurt shakes, however, it was found that preferences

for new foods high in fat content can be learned, and

that conditioning of these preferences is the result of

the postingestive consequences of consumption. It has

been contended that Pavlovian or associative condi-

tioning is central to the acquisition of food prefer-

ences. Because high-fat foods are palatable and

satisfying, which are positive consequences of con-

sumption, children may learn to like these foods.

Such foods are also often used as treats or rewards

for children, which may magnify this preference.

0015 Animal studies suggest that, at least in rats, fat may

be preferred at an early age. Appetite for fat was

measured in 12–15-day-old infant rats. Intake of an

oil emulsion solution was nearly as high as intake of

a dilute sucrose solution (0.03 mol l

1

) or a milk for-

mulation similar to rats’ milk. It was concluded that

the taste for fat is acquired at an early age and fat is

as pleasant to the pups as sweet solutions and

mother’s milk.

0016 In humans, however, there is no evidence to sup-

port the hypothesis that there is an innate, unlearned

preference for fat. Indeed, the possibility of an innate

fat preference seems unlikely because the form and

function of fat are not unitary across food systems.

Furthermore, it has been found that there is no rela-

tionship between taste preferences for high-fat foods

and childhood (< 10 years)-onset obesity, drawing the

conclusion that environmental as opposed to genetic

factors may be more salient determinants of taste

preferences and food choice.

Variability of Fat Preference

0017Gender differences While it is mere anecdote that

‘Jack Sprat would eat no fat and his wife would eat no

lean,’ surveys have provided epidemiologic evidence

that there are, indeed, sex differences in regard to fat

preferences. Although both men and women seem to

find high-fat foods highly palatable, men often derive

the bulk of their dietary fat from meat, especially red

meat, while women derive the bulk of their fat intake

from margarine, whole milk, shortening, and mayon-

naise, and are more likely than men to express prefer-

ences for sweet/fat desserts like cake and icecream.

Such sex differences exist among obese individuals as

well. The favorite foods of obese men and women

were surveyed and it was found that obese men cited

predominantly fat-protein foods (meat dishes) among

their favorites, whereas obese women listed more

carbohydrate/fat sources and more sweet-fat foods

(doughnuts, cake, cookies, and chocolate).

0018Obese/lean differences A possible mechanism for

obesity is that obese persons may have an enhanced

preference for high-fat foods, leading to overcon-

sumption of energy-dense foods. In sensory tests,

obese individuals do, indeed, show a preference for

higher levels of fat in foods than lean individuals.

Several investigators have found that body weight

is related to preferences for fat. It was found that

obese and formerly obese individuals preferred higher

levels of fat in mixtures of dairy products and sugar

than did lean individuals. However, in a later study,

Drewnowski found that only the subset of obese indi-

viduals with a history of large weight fluctuations

showed an enhanced fat preference. Even among

normal-weight individuals, there is a positive rela-

tionship between sensory preferences for fat in a

variety of foods and percent body fat. As body fat

increases, the percent of energy derived from fat in-

creases. In one 3-year longitudinal study, high weight

gain was associated with high fat intake in both men

and women. In all, this work suggests that enhanced

preferences for fat could be important in the develop-

ment and maintenance of obesity; however, no con-

trolled, laboratory-based experiment has studied this

issue directly. Further research is needed to under-

stand how individual differences in preference for

dietary fat influence human food intake and body

composition.

Fat Replacers and Fat Preference

0019There is a theoretical concern about the use of fat

replacers, especially products like sucrose polyester

(SPE), that mimic the properties of fat so closely,

that they may reinforce and maintain the preference

for fatty foods. It can be argued that the most

FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake 2249

effective strategy for fat reduction is to decrease the

preference for high levels of dietary fat. The effects of

two different reduced-fat diets have been studied: one

allow the use of fat replacers and one which did not,

and the effects on the preference for a limited range of

high-fat foods were noted. This study found that the

group which was given low-fat foods without fat

replacers (no fatty sensory qualities) showed a de-

crease in the preferred level of fat in foods, whereas

the group using fat replacers showed no such shift. It

was concluded that the preference for fat in foods is

governed more by exposure to fatty flavors than by

the actual level of fat in foods. It was further sug-

gested that the preference for fat can be lowered, and

that the best strategy for lowering fat preference is,

therefore, to avoid foods with fat replacers. Because

of methodological limitations, however, firm conclu-

sions cannot be drawn from this research. First, he-

donic measures were obtained on only four foods.

Since fat imparts so many different sensory properties

to foods, it appears unlikely that changes in prefer-

ences for fat in one type of food will generalize to

other types of foods. Second, because subjects con-

sumed products at home, there was little control over

the experimental setting. Finally, data were obtained

from self-reported diet records, with scant checks for

compliance.

0020 A recent study measured participants’ sensory

ratings to foods with various levels of fat while they

were consuming diets that varied in overall fat con-

tent: 37, 30, and 26% energy from fat. Participants

rated their sensitivity to and liking for fat in several

foods at baseline, after each 8-week diet period, and

at the end of the entire study. They found no differ-

ences in liking of foods as a function of fat level of the

overall diet. Thus, exposure to a low-fat diet for an

extended period did not diminish fat preference, and

exposure to a higher-fat diet did not increase fat

preference. In this study, however, the low-fat diets

did not use fat-replaced foods exclusively. Thus, al-

though the hypothesis that exposure to fat-replaced

foods may maintain a fat preference may have merit,

further research is needed to investigate this issue

fully.

0021 Energy density Metabolism of dietary fat yields ap-

proximately 9 kcal g, more than twice the yield of

4 kcal g for carbohydrate or protein. There is evidence

that people tend to eat a consistent weight of food.

Given this, the relatively high energy density of fat

would be an important factor in its overconsumption.

For example, 50 g of potato chips (which typically

derive 60% of their energy from fat) provides

269 kcal of energy, while an equal weight of pretzels

(which typically derive about 8% of their energy from

fat or less) provides only 187 kcal. This effect was

tested experimentally in a serving of a milk-based

preload that had varying amounts of water added to

change the volume (300, 450, and 600 ml), while

macronutrient and energy content and palatability

were held constant. The resulting drinks differed solely

in the density of the provided nutrients and energy.

The results showed that the energy density of these

milk-drink preloads affected energy intake at lunch

30 min later, such that intake was significantly lower

(by 18%) after the high-volume, low-energy-density

drink than after the low-volume, high-energy-density

drink. Further, this energy deficit was not compen-

sated for at the dinner meal. Thus, consuming more

energy-dense, higher-fat foods may easily lead to

higher daily energy intakes than eating foods that

are low in fat and less energy-dense.

0022Fat and satiety It has been proposed that fat may be

overeaten because it does not satisfy hunger as well as

other macronutrients. Ingested fat may differ from

ingested carbohydrate and protein in how it affects

such factors as stomach distention, stomach empty-

ing, nutrient absorption, hormonal release, and/or

oxidation of nutrients. Indeed, fat and carbohydrate

have very different postingestive dispositions. In ex-

periments that measured postabsorptive metabolism,

dietary fat was shown to be metabolized much more

slowly than carbohydrate or protein. Carbohydrate

ingestion produces rapid rises in blood glucose, while

fat ingestion often depresses blood glucose. The ‘glu-

costatic theory,’ which suggests that the sensation of

hunger is maintained until blood glucose levels reach

adequate levels, would posit that carbohydrates pro-

duce more rapid satiety than fats. Opponents of the

glucostatic theory argue that there are other, more

important factors influencing satiety, including the

release of ‘satiety hormones.’

0023One such putative satiety hormone is cholecysto-

kinin (CCK). CCK is particularly released when

amino acids and/or some types of fat enter the small

intestine. Thus, the ingestion of fat could lead to early

satiety despite having less of an effect on blood

glucose than carbohydrates. Because of these

differing physiological effects, it is difficult to make

any definitive statements regarding the satiety value

of fat versus carbohydrate. However, data from con-

trolled-laboratory feeding studies suggest that, for

some people, carbohydrate may be more satiating.

One group reviewed various studies that utilized a

preloading model (giving fixed amounts of macronu-

trients and assessing the effects on subsequent satiety/

hunger and food intake) to detect any differences in

the satiety value of fat versus carbohydrate. They

concluded that carbohydrate seems to have greater

2250 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

satiety value than fat in individuals with certain sub-

ject characteristics (e.g., obese and those concerned

with their body weight). Overall, however, there is

little evidence that carbohydrate is more satiating

than fat, and additional research is needed to deter-

mine if overconsumption of fat is related to a physio-

logical insensitivity to the amount of fat in food or

other factors.

Types of Fat Replacers

0024 The National Heart, Lung, and Blood Institute of the

National Institutes of Health recommends that the

food industry accelerate its efforts to develop and

market foods reduced in total fat, saturated fat, and

cholesterol content. The food industry response has

been vigorous. Recent advances in food science and

technology have led to the development of reduced-

energy and energy-free, fat-like substances. The use of

these substances in foodstuffs provides consumers

with new options for highly palatable, lower-energy,

low-fat products. The American Dietetic Association

(ADA) favors the use of these products for consumers

seeking to reduce dietary fat intake and perhaps body

weight. The ADA’s 1991 position paper on fat

replacements states: ‘the ADA recognizes the innova-

tive development and use of traditional food ingredi-

ents and processing methods to reduce or replace fat

in foods’.

0025 Fat replacers comprise a diverse range of chemical

and processing sources; they possess varied sensory,

functional, and physiologic properties. Some of the

currently used and newly developed fat replacers are

described below. Table 1 provides a summary of the

replacers and their characteristics.

Carbohydrate- and Protein-Based Fat Replacers

0026 Several carbohydrate- and protein-based materials

are presently in use. These substances generally add

bulk, viscosity, or structure to a food by stabilizing

water into a gel-like structure. In contrast, micropar-

ticulated protein mainly provides a textural continu-

ity (often associated with fat). Because it consists of

particles so small that the units are undetectable by

oral sensory systems, microparticulated protein gives

the illusion of a creamy, smooth texture. Protein-

based fat replacers can also provide bulk and viscosity

characteristics similar to carbohydrate fat replacers

and can supply added functionality to food systems,

including opacity and emulsification. These products

are partially or fully digestible and provide between

1 and 4 kcal g.

0027 Unfortunately, protein- and carbohydrate-based

materials are very limited in their functional usage

in general fat replacement. Both types of fat replacers

can only be used in a few categories of food (e.g.,

dairy products, dressings, spreads, cold applications,

and some meat products); further, some are not well-

suited for baking application, cannot be used to fry

foods, and have a limited shelf-life due to high water

content. Most of the carbohydrate- and protein-based

fat replacers cannot be used for the development of

lipid-associated flavors or flavor modification in

foods; microparticulated protein-based fat replacers,

in contrast, do have a clean flavor base and good

flavor-release qualities. Studies indicate that protein-

and carbohydrate-based replacers pose little or no

toxicological risk when used in the moderate quan-

tities proposed.

Lipid-Based Fat Replacers

0028One lipid-based fat replacer is currently being market-

ed (olestra or Olean) and others are under develop-

ment. Lipid-based fat substitutes have the advantage

of having similar functional and sensory properties to

the fats they replace. Thus, the potential applications,

in contrast to carbohydrate- or protein-based sub-

stances, include most or all areas where fat and oils

are presently used.

0029SPE or olestra, its generic name, is a fat-like mater-

ial compound of hexa-, hepta-, and octa-esters of

sucrose and long-chain fatty acids. Its physical prop-

erties are nearly identical to those of conventional

dietary fats. Because of the molecular bonds in SPE,

it cannot be hydrolyzed by pancreatic lipases, and the

large molecule, consequently, cannot be absorbed

through the intestinal mucosa. Because SPE is not

digested or absorbed, it passes through the gastro-

intestinal tract intact and is excreted in the feces,

adding no energy to the diet.

0030Caprenin, another lipid-based fat substitute, con-

sisting of a glycerol molecule esterified with caprilyc,

capric, and behenic acids, was developed for use in

chocolate. Unlike SPE, the glycerol-based molecule is

hydrolyzable by pancreatic enzymes, but provides

only 5 kcal g (instead of the 9 kcal g of triglyceride)

due to the poor absorption of behenic acid. Other

low-calorie fat replacers include Salatrim (5 kcal g)

and Aldo MCT, Captex, and Neobee (8.3 kcal g).

Other lipid-based fat replacers include partially and

poorly digested organic compounds. A list of such fat

replacers can be found in Table 1.

Other Fat Replacers

0031Polyglycerol esters form an intermediate category be-

tween lipid-based and nonlipid-based fat replacers.

The functional metabolic properties of polyglycerol

esters range between carbohydrate- and lipid-

based fat replacers, depending on their level of ester-

ification. Polyglycerols may be partially or wholly

FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake 2251

tbl0001 Table 1 Types of fat replacers

Composition Chemical name/process (if any) Trade name/company Applications

Carbohydrate-based

Starch-based Modified starch Amalean Cheesecake, pourable salad dressings, sauces,

cream fillings, dips, spreads, bakery, dairy products,

meat and poultry products, icecream, yogurt

Leanbind

N-Lite

PureGel

Sta-Slim

Maltodextrin C*Pure Extruded products, bakery products, dressings, sauces,

spreads, frozen desserts, toppings, cakes,

buttercream and fillings, snacks

CrystaLean

Lycadex

Maltrin

Novelose

Hydrolyzed flours Enzymatically and

acid-hydrolyzed flour

Quaker Oatrim Processed meats, bakery, prepared foods, baby foods,

sauces, cheese spreads, cream cheeseRice-gel

Rice-trin

Fiber-based Celluloses and

hemicelluloses

Avicel Ac-815 Mayonnaise, salad dressings, butter substitutes, cheeses,

sour cream substitutes, spreads, bakery productsCellulon

Ex-cel

Fibrex

Just Fibre

Fructose polymers Inulin Raftiline Icecream, cheese spreads, chocolate, dressings, meat

Fibruline

Gums Gellan gum Kelcogel range Margarines, spreads, cakes, cookies, dips, frozen desserts,

salad dressings, sauces, gravies, instant products, soups,

toppings, canned foods, frozen foods

Xanthan gum Ketrol range

Gelamix

Rhodigel

Acacia gum Spraygum

Guar gum Procol range

Supercol F

Gels Carrageenan Aquagel Bakery products, beverages, sauces, confectinery,

dairy products, salad dressings, meat productsBenGel

Liangels

Protein-based

Whey protein Dairy-Lo Frozen desserts, dairy products, baked goods,

salad dressings, spreads, sauces, toppings, frostingDairylight

Nutrilac

Simplesse

Trailblazer

Soy protein Soy protein Meat and dairy products, patties,

hamburgers, frankfurters, cream cheeseConcentrate

Supro range

Milk protein Complete Milk Yogurt and cultured products, dressings,

mayonnaise, sauces, dipsProtein

Lactalbumin

Lactomil

Miprodan

Microparticulated zein

protein (from corn gluten)

Lita Frozen desserts, mayonnaise, sour cream, salad dressing,

whipped topping, milk, yogurt, confectionery and chocolate

Lipid-based

Low-calorie fats Medium-and long-chain

triglyceride molecules

Aldo MCT Chocolate, chocolate coatings, confectionery products,

replacement for liquid vegetable oils in productsCaprenin

Captex

Neobee M-5

MCT Oil

Salatrim

Synthetic fats Sucrose polyester Olestra Cooking and frying utilities.

Colestra Currently only approved for use in savory snack foods

Other esters Alkyl glycoside fatty

acid polyesters

Carboxy/carboxylate esters

Dialkyl dihexadedecyma

lonate (fatty acid ester)

Polyhydroxyl esters

Baked goods, chocolate flavored products,

frozen deserts, margarine, meats,

salad dressings, snack foods

digestible, but are generally used in low concentra-

tions relative to the quantity of fat they replace as part

of an aqueous emulsion.

Low-Fat Diet Research

0032 Fat replacers are a relatively recent development in

the field of studying dietary fat intake. Thus, much of

the research regarding dietary fat intake predates the

development of many fat replacers. This section

reviews research involving manipulations of dietary

fat intake with and without fat replacers. Some stud-

ies have reduced the fat content of the diet by using

foods naturally or intrinsically low in fat (fruits, vege-

tables, and grains). Others have used specific fat-

replaced foods available at the time of study or

a combination of naturally low-fat foods and fat-

replaced foods. The following studies will serve to

illustrate the effects of reducing the fat content of

the diet on both energy and fat intake.

Short-Term Dietary Fat Manipulation

0033 A number of studies have investigated the effects of

manipulating the fat content in certain meals on

energy intake on a short-term basis (5 days). One

such study manipulated the energy and fat content of

a midday meal for 5 days by using intrinsically low-

fat foods, as well as some commercially available

reduced-fat foods. They found that both men and

women compensated for energy dilutions in the diet.

Interestingly, compensation for excess of energy

intake was weaker, especially when the additional

energy was derived from dietary fat. Unfortunately,

the data for fat intake were obtained via diet records,

and such data must be interpreted cautiously due to

the potential errors and biases inherent in self-

reported measures. However, similar results were

obtained in a well-controlled residential laboratory

study that manipulated the carbohydrate and fat con-

tent of certain meals. Participants (lean males) com-

pensated well and quickly for the caloric dilution in

this study, but when the energy level was again raised

to baseline levels, participants did not compensate

and consequently overate. In a subsequent residential

study that studied the affect of altering fat and

carbohydrate content of a lunch meal using four con-

ditions (high-fat, high-carbohydrate, low-fat, low-

carbohydrate; with 3 days per condition), energy

compensation was observed regardless of macronu-

trient composition (mean daily energy intakes: 2824,

2988, 2700, and 2890 kcal respectively). However,

energy intake from dietary fat was fairly constant in

all conditions except the high-fat condition, which

resulted in significantly greater energy intake than

the other three conditions. These studies suggest

that decreasing the fat (and thus the energy) content

of the diet will result in compensation for energy in

subsequent meals or snacks, but not for fat. Further-

more, there is some evidence that when additional

fat is included in the diet, it is unlikely that a spontan-

eous reduction in energy and fat intake will occur to

compensate for this surfeit. It is important to note that

these findings are dependent on both the magnitude of

the manipulation (amount of fat/energy reduction)

and the characteristics of the study participants (e.g.,

lean/obese, restrained (concerned about body weight)/

unrestrained (not concerned about body weight)).

Longer-Term Manipulations

0034The studies discussed above manipulated fat intake

within specific meals or over the course of a day. This

type of intervention provides useful information

about short-term regulation of fat and energy intake

when dilutions and surfeits are encountered in spe-

cific meals or snacks, but they provide no information

about long-term regulation of fat and energy intake

or the ability to maintain compliance with a low-fat

diet. In contrast, a few naturalistic studies have exam-

ined the effects of reducing intake of dietary fat in

certain groups over a longer timeframe. These studies

utilized various strategies, including nutritional coun-

seling, behavioral therapy, and financial incentives, to

aid subjects in reducing their dietary fat consumption.

These studies generally found that the intervention

groups did consume less dietary fat than control

groups. Intervention periods in these studies ranged

from 12 to 20 weeks. These studies suggest that

compliance with a low-fat diet can be maintained

over at least this moderate amount of time. There

are few data, however, regarding longer-term compli-

ance with a low-fat diet. One group of researchers

followed 303 women participating in the Women’s

Health Trial for 1 and 2 years. These women either

received no specific intervention or intensive instruc-

tion in maintaining a low-fat diet by such means as

reducing cooking fats, substituting low- or no-fat

variants of high-fat foods and increasing traditional

low-fat foods in the diet. After 1 year, the intervention

group had reduced their dietary fat intake by 45% of

their baseline intake and energy intake by 59%. Most

of the reduction occurred within the first 6 months of

the intervention and was maintained at 1- and 2-year

follow-up. Results of naturalistic studies such as these

are often used as a basis for advocating low-fat diets

and that compliance to low-fat diets can be main-

tained over time. However, although these studies

may have validity, they relied heavily on self-report

(diet records or food-frequency questionnaires) as a

source of data on fat intake, and should be interpreted

cautiously.

2254 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

0035 Laboratory-based experiments provide more ac-

curate intake measurements and stringent controls

over the experimental setting. Three controlled la-

boratory studies have investigated the effects of

high- and low-fat diets on energy intake and body

weight over varying periods of time. The first study

allowed lean and obese participants to consume a

low-energy-density diet comprised of intrinsically

low-fat foods (fruits, vegetables, and whole grains)

or a high-energy density diet ad libitum for 5 days

(0.7 vs 1.5 kcal g). Both obese and nonobese groups

significantly reduced their energy consumption on the

low-energy diet. Nearly twice as many calories were

consumed during the high-energy-density diet com-

pared to the low-energy-density diet (3000 vs

1570 kcal day). Weight change data were not

reported.

0036 Two other studies, both conducted at Cornell, are

often cited in both scientific and popular literature as

proof that ad libitum consumption of low-fat foods

can reduce fat intake and produce weight loss. The

low-fat diets in these two studies included fat-

replaced foods (a limited selection of margarines,

salad dressings, and mayonnaises available at the

time the studies were conducted) as well as intrinsic-

ally low-fat foods. In the first of these studies, all food

(meals and snacks) was provided for 24 women

divided into two groups: < 101% ideal body weight

(IBW) and > 101% IBW. Each participant was fed

three diets (in a counterbalanced order): low-fat

15–20%, medium-fat 30–35%, and high-fat

45–50% of energy. Participants could eat the foods

ad libitum. Each diet was fed for 14 days with a 7-day

washout between test periods. Energy consumption

was found to be positively correlated with the level

of dietary fat: total daily energy consumed on the

low-fat diet averaged 2087, the medium-fat diet

2352, and the high-fat diet 2614 kcal. Over the

2-week intervention periods, the diets did not pro-

duce any statistically significant weight changes.

0037 The second Cornell study was similar, but extended

the intervention period to 11 weeks. It is unclear

whether normal-weight or obese women were stud-

ied: although a mean subject height is reported, no

mean weight is reported, though it is noted that

individuals < 101% of IBW (according to Metropol-

itan Life standards) were excluded. This study exam-

ined two diets: one was comprised of 20–25% energy

from fat (low-fat) and the other, 35–40% energy from

fat (control). Again, the women were allowed free

access to foods. It was found that participants con-

sumed an average of 286 fewer kcal day on the low-

fat diet. In contrast to other Cornell study, these

participants did lose weight on both diets (low-fat:

2.54 kg and control: 1.26 kg). There were no

reasons given by the authors for the weight loss on

the control diet.

0038A longer-term animal study examined the impact of

replacing fat using a carbohydrate-derived fat re-

placer on three groups of 20 female Sprague-Dawley

rats. The rats were chronically fed either a high-fat

diet (45% energy from fat) or a low-fat diet (25%

energy from fat) containing either no added fat re-

placer (control diet) or the maltodextrin, Paselli. The

three diets differed in texture. Rats were fed the con-

trol diet for 10 days, and were then divided into three

groups, receiving one of the three diets for 42 days.

Preference tests for the three diets were assessed

before and after the 42-day period. It was found

that all but two of the rats preferred the diet with

the fat replacer over the high-fat and control diets,

and that food intake was the greatest in the group

fed the fat-replacer diet (741 g per 58 days ¼control,

736 g per 58 days ¼high-fat, 900 g per 58 days ¼fat

replacer). However, energy intake was greatest in

the group fed the high-fat diet (3250 kcal per 58 -

days ¼control, 3871 kcal per 58 days ¼high-fat,

3585 kcal per 58 days ¼fat mimetic). The higher

energy intakes of the high-fat and fat replacer-fed

animals resulted in greater weight gain during the

experimental period compared with control rats,

largely due to an increase in fat mass. These data

suggest that the inclusion of highly preferred, fat-

replaced foods in the diet may result in a reduction

in fat intake, but consumption of such foods is not

associated with reductions in energy intake.

0039Overall, the evidence from the human studies

presented here indicates that low-fat diets are poten-

tially useful for reducing both total energy intake

and the amount of fat consumed. While these early

results have some validity, their interpretation is often

oversimplified. It is important to recognize that the

methods available to assess the effects of low-fat diets

have limitations that may influence outcome. Par-

ticipants in the three laboratory-based studies

reviewed above allowed subjects to consume food

ad libitum during the dietary interventions; however,

this access was limited to the particular fat-level

that was under study. Thus, during a low-fat condi-

tion, the subjects could only choose from low-fat

foods, while in the high-fat condition, only high-fat

choices were available. Although the subjects rated

the high- and low-fat diets equally palatable, this

does not mean that, given a choice, they would vol-

untarily eat the low-fat foods, making it difficult to

determine if the findings are applicable to free-living

individuals. As demonstrated in the animal study

described above, even when restricted to a highly

palatable low-fat diet, overall energy intake may not

be reduced.

FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake 2255

Labeling Effects of ‘Low fat’

0040 A further limitation of these initial studies is that they

did not provide participants with any information

(nutritional or otherwise) about the foods that they

were eating. Food products labeled with claims such

as ‘lite,’‘reduced-fat,’ and ‘fat-free’ send powerful

messages to the consumer. The results of the low-fat

diet studies cited above might be different for individ-

uals who are aware of whether their diet is low or

high in fat or who knowingly choose to substitute a

low-fat food for a high-fat food outside an experi-

ment. A few studies have examined the impact of such

information on subsequent food intake. It was found

that intake at a self-selection meal was higher

following a yogurt preload labeled ‘low-fat’ than

following equicaloric yogurt preloads labeled ‘high-

fat.’ Another study fed 96 men and women a snack of

potato chips made with olestra or triglyceride every

afternoon for 2 weeks in a counterbalanced order.

Half of the participants were given full nutrition

labels about the potato chips and the other half

were given bags that simply said ‘potato chips.’ Inter-

estingly, in the group that received no nutrition infor-

mation about the chips, all participants ate the olestra

and the triglyceride potato chips in similar quantities.

In the group that received information, a subset of the

participants, those who are very concerned about their

body weight and tried to control their food intake (as

measured by the Three Factor Eating Questionnaire),

consumed significantly more olestra potato chips

(60 + 7 g) than regular potato chips (50 + 17 g).

Other subgroups (obese/normal weight; male/female)

did not eat the chips in different quantities. Results

from these studies indicate that information about fat

(and energy) content can influence intake of the low-

fat food itself or of food eaten subsequently. It is

apparent that cognitive processes can override or

interact with physiological processes in regard to

food intake and, therefore, play an important role in

energy balance. It may be those who are the most

restrictive in their dietary choices who may be at

most risk for overconsuming fat-free and reduced-

fat foods.

0041 Cognitive processes may also be involved in the

phenomenon of food intake being controlled by

weight or volume rather than by its energy content.

In other words, individuals may control how much

they eat by setting a ‘standard portion size’ of food

consumed rather than a ‘standard energy amount.’ As

discussed previously, it is likely that it is the low-

energy density of the diets provided in these low-fat

diet studies and not a physiological satiety mechan-

ism that accounts, at least in part, for the differences

in the amount of energy consumed. In each of these

studies, subjects ate similar gram weights of food on

both low-fat and high-fat diets. It is likely that sub-

jects are eating a ‘standard’ weight or volume rather

than specifically responding to the covert energy ma-

nipulation. Thus, a diet of low energy density con-

sumed in equal amounts to a higher-density diet

would provide less energy. Fat-replaced foods may

have their greatest impact on fat and energy intake

by simply reducing the energy density of the foods we

consume.

0042There is evidence that energy intake may be more a

function of the energy density of the diet than the

actual fat content. Three studies have found that

energy intake is constant despite variations in fat

content when the energy density of the diet is held

constant. Given this robust effect, a group of

researchers investigated the effects of varying the

energy density of the diet while holding fat content

constant. This manipulation was achieved primarily

by altering the water content of foods. The research-

ers then fed normal-weight women all of their meals

in a laboratory setting over three 2-day periods using

three levels of energy density in provided entre

(low ¼1.03 kcal g

1

; medium ¼1.17 kcal g

1

; and

high ¼1.34 kcal g

1

). The women, like participants

in the earlier studies, ate a constant weight of food

across the dietary conditions, resulting in a 30% de-

crease in energy intake in the low-energy-density con-

dition compared to the high-energy density condition;

however, there were no corresponding changes in

ratings of hunger and fullness. These results provide

clear evidence that alteration in energy density of

food can affect energy intake. Similar studies need

to be done to investigate the effect of using foods

made with fat replacers to reduce energy density

instead of water.

0043If fat-replaced foods are consumed in much greater

quantities than their high-fat counterparts, however,

this net energy reduction will be nullified. The belief

that one can consume an unrestricted amount of low-

or no-fat food and still expect to bring about desirable

dietary change and/or weight loss or maintenance

is not supported by the animal or human literature.

For example, Sprague-Dawley rats were fed high-fat

(41% energy from fat) or fat-free (0% energy from

fat) pound cakes in addition to chow for 30 days. The

fat-free pound cake was prepared with nonfat milk

and egg whites, and used modified cornstarch,

xanthan gum, and guar gum to simulate the orosen-

sory properties of fat. Rats fed the high-fat cake and

chow consumed more energy (P < 0.05) and gained

more weight (P < 0.05) than did rats fed fat-free cake

and chow. The rats fed the fat-free cake, however,

overate and gained more weight than did the chow-

only controls. The authors concluded that removing

2256 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

the fat from the cake reduced, but did not eliminate,

its obesity-promoting effects, and that low-fat diets

have to be consumed in moderation if used for weight

control purposes.

0044 To examine the question of whether isolated reduc-

tion of fat with no other dietary restriction leads to

weight loss in humans, the effects of a low-fat diet

consumed ad libitum were compared with a low-fat

diet with caloric restriction. It was found that partici-

pants on the calorically restricted, low-fat diet lost

significantly more weight and reduced fat intake to a

greater extent than those on the low-fat diet con-

sumed ad libitum. Hence, advocating that an individ-

ual can eat as much as he/she desires and lose weight

as long as the food is low in fat content is unwar-

ranted based on these data. For maximum weight

control, total energy intake must also be restricted

below energy needs.

0045 Another important question is whether varying the

fat content, while keeping energy equal, of an energy-

restricted diet enhances weight loss. This question

was addressed by an animal study. It was found that

when rats previously maintained on a high-fat diet

(40% of energy) were switched to equicaloric diets

(75% of their previous ad libitum intake) that varied

in fat content (12, 28, or 45% fat), rats fed the 12%

fat diet lost significantly more body fat than the rats

fed the 45% fat diet. These results indicate that, at

least in rats, an energy-restricted diet produces

greater weight loss when it is also low in fat. Al-

though similar data are not available for humans, if

weight loss is the goal, it is reasonable to recommend

restriction of both dietary fat and overall energy

intake to achieve the maximum benefit. Thus,

reduced-fat foods will enhance weight loss if an indi-

vidual who is consuming greater than 30% of energy

from fat restricts food choices to those low in fat but

not high in energy, while keeping the volume of food

consumed constant.

Fat-Replaced Foods and Disease Risk

0046 Although the usefulness of fat-replaced foods for

energy reduction and weight loss requires further

investigation, it is reasonable that reductions in diet-

ary fat may be helpful in reducing the risk of diseases

associated with high fat intake, such as cardiovascu-

lar disease and type 2 diabetes. In a recent study, 30

men and women (15 of whom had diabetes) were

supplied with five low-fat or fat-free products or

their regular fat counterparts and asked to consume

them as part of their regular diet in a free-living, free-

choice setting for 3 days. No difference was found in

usage of the fat-modified foods between people with

or without diabetes. Participants consumed the

fat-replaced foods in similar quantities to the full-fat

counterparts, which resulted in a significant reduc-

tion in overall fat (g) intake, but total energy intake

was not different between the fat-modified and the

full-fat conditions. Cholesterol and saturated fat

intake were also significantly lower in the low-

fat condition than in the full-fat condition. It has

been shown that foods made with fat replacers

were less acceptable than foods made with sugar

replacers among participants diagnosed with dia-

betes. Foods made with olestra were less acceptable

still than foods made with fat replacers in general. In

a recent survey, it was found that knowledge about fat

replacers, fat-replaced foods, and general nutrition

was poor among individuals with type 2 diabetes.

Respondents were much more familiar with sugar

replacers than fat replacers. Thus, despite evidence

that inclusion of fat-replaced foods may be helpful

for people with diagnoses such as type 2 diabetes,

knowledge about and acceptance of such foods are

low.

Noncaloric, Lipid-Based Fat Substitute

Research

0047Because noncaloric, lipid-based fat substitutes have

the greatest potential range of applications as fat

replacers, it is important to review the current re-

search on the effects of consuming these materials

on food intake and body composition. At this time,

only olestra (Olean) is approved for use by the Food

and Drug Administration in the USA. Olestra’s ap-

proval is limited to applications in savory snacks.

0048Animal studies comparing varying levels of fat and

SPE have demonstrated that the higher the percentage

of energy from fat in the diet, the greater the fat intake

and, in some cases, the body weight. For example, in

one study mature female Sprague-Dawley rats were

fed five diets that varied in fat content: control diet

(21%), low-fat diet (2%), high-fat diet (63%), and

two medium-fat diets (30% and 51%) fat. The rats

compensated for the low-fat diet compared to the

control diet by increasing food intake, resulting in

no difference in overall energy intake. However,

when the control diet was replaced with the high-fat

diet, the rats became obese and hyperinsulinemic.

When rats fed the high-fat diet were switched to the

medium-fat diets, they also increased food intake to

compensate for the energy reduction. These rats were

more obese than control rats, but less obese than the

rats fed the high-fat diet, suggesting that a modest

reduction in dietary fat content can attenuate fat’s

obesity-promoting effects. In another animal study,

the effect of SPE replacement was examined on

the body weights of lean and obese Zucker rats by

FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake 2257