Physiology&Behavior,Vol. 49, pp. 803--810. © Pergamon Press plc, 1991. Printed in the U.S.A.
0031-9384/91 $3.00 + .00
Soft Drinks With Aspartame: Effect on Subjective Hunger, Food Selection, and Food Intake of Young Adult Males RICHARD M. BLACK,*t
PHYLLIS TANAKA,*
LAWRENCE
A. L E I T E R * t
A N D G. H A R V E Y A N D E R S O N .1
*Department of Nutritional Sciences, #Department of Medicine, "~Department of Psychiatry Faculty of Medicine, University of Toronto, Toronto, Canada R e c e i v e d 15 M a y 1990 BLACK, R. M., P. TANAKA, L. A. LEITER AND G. H. ANDERSON. Soft drinks with aspartame: Effect on subjective hunger, food selection, andfood intake of young adult males. PHYSIOL BEHAV 49(4) 803-810, 1991.--Ingestion of aspartame-sweetened beverages has been reported to increase subjective measures of appetite. This study examined the effects of familiar carbonated soft drinks sweetened with aspartame on subjective hunger, energy intake and macronutrient selection at a lunch-time meal. Subjects were 20 normal weight young adult males, classified as either restrained or nonrestralned eaters. Four treatments of carbonated beverages included 280 ml of mineral water, one can of a soft drink (280 ml) consumed in either 2 or 10 minutes, or two cans of a soft drink (560 ml) consumed in 10 minutes, administered at 11:00 a.m. Subjective hunger and food appeal were measured from 9:30 a.m. to 12:30 p.m., and food intake data were obtained from a buffet lunch given at 12:00 noon. There were no treatment effects on energy intake, macronutrient selection or food choice at the lunch-time meal, or food appeal, though restrained eaters consumed more than nonrestralned eaters in all four treatment conditions. Consumption of two soft drinks (560 ml, 320 mg aspartame) significantly reduced subjective hunger from 11:05 a.m. to 11:30 a.m. compared to one soft drink (280 ml, 160 mg aspartame) or 280 ml of mineral water. Thus ingestion of soft drinks containing aspartame did not increase short-term subjective hunger or food intake. Aspartame
Subjective hunger
Human behavior
Feeding
THE nonnutritive sweetener aspartame (APM) is becoming an increasingly popular sucrose substitute in foods and beverages. However, when such high intensity sweeteners are used as replacement for nutritive sweeteners in foods and beverages, the effect on food intake is uncertain. There are various reports suggesting that such replacement may reduce (13, 25, 33), have no effect (8,15) or even enhance food intake (4, 20, 21). The possibility of enhancing food intake through consumption of nonnutritive sweeteners was raised by reports of an increase in subjective hunger following sweetener ingestion in water [e.g., (4,21)], in yoghurt (20), as the sole sweetener in unflavored gum (30) and by the correlation of nonnutritive sweetener usage with increased rate of weight gain in an epidemiological study (28). The putative mechanism for the appetite-enhancing effect of nonnutritive sweeteners has been elicitation of a cephalic response resulting from the taste of the sweetener (20,30). Cephalic responses can stimulate insulin release, increasing glucose uptake by tissue, which in turn reduces blood glucose levels and ostensibly stimulates appetite [cf. (14, 17, 18, 32)]. It has been hypothesized that, in contrast to nutritive sweeteners, nonnutritive
sweeteners elicit this cephalic response without providing energy, and so the stimulated appetite is not assuaged (20,32). In addition to increases in subjective hunger, increased food intake arising from the consumption of a food with added nonnutritive sweeteners has also been reported. One hour after ingestion of a saccharin-sweetened yoghurt preload, subjective ratings of hunger increased as did lunch-time intake and total calories consumed during the remainder of the day, compared to consumption of an unsweetened yoghurt preload (20). However, others have failed to find any effect of the addition of nonnutritive sweeteners to food on energy consumption, for example when added to a breakfast cereal (15), or pudding or jello (25). It has been suggested that this failure to observe any appetite enhancement after consuming nonnutritive sweeteners may have been due in part to the use of foods as the vehicle rather than beverages [as in the initial positive finding (4)] (26). However, both short-term (18,26) and long-term (31) studies have failed to uncover any appetite or food intake enhancement associated with consumption of nonnutritive sweeteners in flavored beverages. In the previous experimental studies involving beverage con-
1Requests for reprints should be addressed to Dr. G. H. Anderson, Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, 150 College St., Toronto, Ontario, Canada M5S 1A8.
803
804
BLACK ET AL.
sumption and the acute response on appetite and food intake, the nonnutritive sweetener has been provided as a beverage or snack, generally 30 to 60 minutes prior to presentation of a lunch-time meal. It is important to note that, without exception, these studies did not control for time since, macronutrient content of, or energy content of, the previous meal, i.e., breakfast. As such, subtle effects on appetite engendered by the nonnutritive sweetener may have been masked. Furthermore, while some have attempted to relate their f'mdings to consumption of commercially available soft drinks containing nonnutritive sweeteners such as aspartame [cf. (15, 19, 26)], no direct tests of the effects on appetite of consuming such soft drinks have been conducted. Therefore, the present study strictly controlled timing and size of the breakfast meal on test days, and delivered the nonnutritive sweetener aspartame in a commercially available soft drink, commonly referred to as a diet soft drink. We report herein the effects of both volume and duration of exposure to diet soft drinks on subjective measures of hunger and on lunch-time food intake.
TABLE 1 EXPERIMENTAL SCHEDULE Time
Procedure
10:00 p.m. (night before) 7:45 a.m. 8:00 a.m. 9:30 a.m. 10:55 a.m. 11:00 a.m.
11:05 a.m. l h l 0 a.m. 11:15 a.m. 11:20 a.m. 11:30 a.m.
METHOD 11:45 a.m.
Subjects
12:00 p.m.
Twenty male subjects [ n = 2 0 , age 19 to 25 years, Body Mass Index (BMI, weight/height 2, units are kg/m 2) 22 to 29] participated in the study. Subjects were recruited by posters placed throughout the University of Toronto and by word of mouth. Excluded from the study were those who smoked, followed a vegetarian diet, or had a diagnosis of phenylketonuria, a food allergy, a major medical illness, or received medications. The subjects gave informed consent to participate in the study, approved by the University of Toronto Human Subjects Review Committee.
12:05 p.m. 12:30 p.m.
Procedure Upon recruitment, subject weight and height were measured. Each subject also completed the Restrained Eaters Test (9), as well as a Food Liking Checklist and a Food Acceptability List, from which an individualized buffet lunch menu was prepared. Subjects also indicated a preferred soft drink flavour from a choice of Sprite, 7-UP, orange, ginger ale or cream soda, to be consumed during the study. The full experimental schedule is described in Table 1. Subjects were required to fast from 10:00 p.m. the previous night until breakfast was provided. Subjects arrived at the feeding studies laboratory in the Department of Nutritional Sciences, University of Toronto, at 7:45 a.m. Each subject was then presented with a breakfast meal (Table 2) to be entirely consumed within 30 minutes. The breakfast meal was individually tailored to each subject's weight, so that it provided 25% of the average daily caloric intake, based on tabulated estimates of average energy expenditure (e.g., 3000 kcal/day for a 71-kg man of average height and age range) (7). Breakfast calories were adjusted for an individual's weight by altering the amount of cereal and milk presented for consumption. Measures of subjective appetite and food preference were taken throughout the morning (Table 1). Four treatments were administered at 1 h 0 0 a.m., with treatment order being fully randomized across subjects (Table 3). Subjects were unaware of the nature of the soft drink, i.e., regular or diet. Soft drinks of the predetermined flavor preference for the individual were served cold (5°C) in 300-ml plastic cups. Subjects were required to consume all of the beverage provided within the time allotted. Lunch was provided at 12:05 p.m. Each subject was served an individualized buffet lunch, prepared in a visually appealing man-
Subject fasts Subject arrives at Feeding Studies Laboratory Subjects consume breakfast VAS Motivation to eat VAS Food Appeal VAS Motivation to eat VAS Food Appeal Treatment (preload) VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Food Appeal VAS Motivation to eat VAS Motivation to eat VAS Food Appeal Buffet lunch served VAS Motivation to eat VAS Food Appeal Beverage Consumption checklist*
*To be answered after completing final test session only. ner and served in excess, and instructed to eat until comfortably full. Subjects were allowed 30 minutes to complete their lunch. Lunch size was sufficient to ensure that no subject would consume all that was offered in total, or of any one item. While individual lunches varied in the foods that were presented, overall macronutrient content was essentially constant across lunches. For any given subject, the buffet lunch was the same at each test session. A typical lunch menu is presented in Table 4.
Dependent Variables Food intake and selection. At the end of each lunch, food consumed was measured and total calories consumed were calculated. The number of calories consumed as protein (PRO), carbohydrate (CHO) and fat (FAT) were also calculated. Macronutrient
TABLE 2 COMPOSITION OF AN AVERAGE BREAKFAST
Food
Quantity
kcal
PRO g
CHO g
FAT g
Shreddies 2% milk Oat-bananaraisin muffin Orange juice
250 ml 175 ml 2 small
209 96 330
5.1 6.4 6.0
46.1 9.3 58.0
0.4 3.7 10.0
250 ml
118
1.8
28.4
0.2
753
16.4 (8%)
141.8 (75%)
14.3 (17%)
Optional coffee was available with a maximum addition of 10 g sugar and 30 ml milk = 50 kcal.
SOFT DRINKS WITH ASPARTAME
805
TABLE 3
10-cm line word anchored at each end. Subjective appetite was assessed with the aid of four different VAS's which measured 1) desire to eat, 2) hunger, 3) fullness, and 4) prospective consumption (27). The food appeal VAS measured the appeal (no appeal at a l l . . , very appealing) of 32 commonly available foods. Portion sizes were equated for energy content. These foods were classified by principal macronutrient component (i.e., protein, carbohydrate, fat or low calorie, 8 foods per classification for a total of 32 foods) (21).
EXPERIMENTAL DESIGN AND ASPARTAME CONTENT OF SOFT DRINKS
Treatment A B C D
Aspartame (rag)*
Preload 280 ml Carbonated Water (control) 280 ml Diet Soft Drink 280 ml Diet Soft Drink 560 ml Diet Soft Drink
Consumption (rain)
0
2
160 to 170 160 to 170 320 to 340
2 10 10
*Precise amounts depended upon the diet pop consumed.
composition of the foods was determined by chemical analysis results obtained through the manufacturer when possible, and otherwise from food composition tables. Because the foods were of relatively constant composition (with the possible exception of the fat content of the beef), it was assumed that any minor errors in macronutrient composition and total energy content reported in the food tables would not contribute substantially to the within subject variability on test versus control days. Foods chosen at the lunch-time meal were placed in the following categories: bread, meat, dairy, condiment, or dessert. Calculation of the energy content of foods (kcal) consumed from each category allowed determination of any treatment effects on selection of these foods. Visual analogue scales. Measurement of subjective appetite and food appeal were made throughout the morning using visual analogue scales (VAS) (Table 1). Each VAS was a continuous
TABLE 4 TYPICAL BUFFET LUNCH MENU
Food or Beverage Bread: Whole Wheat Meat: Ham Turkey Bologna Dairy: Cheese (cheddar) Milk (whole) Orange juice Water Condiments: Butter Mayonnaise Mustard Lettuce Dessert: Chocolate chip cookies Oatmeal cookies Oreo cookies Shortbread cookies Sara Lee Pound Cake Sara Lee Chocolate Fudge Cake
Amount
324.0 g (10 slices) 101.5 g ( 5 slices) 108.8 g ( 5 slices) 217.6 g (10 slices) 232.4 g 250 ml 250 ml 250 ml 30 g 60 g 15 g 4 leaves 5 cookies 5 cookies 5 cookies 5 cookies 3 cakes (46 g each) 3 cakes (46 g each)
Data Analysis General. The primary analysis was conducted as follows. First, an ANOVA involving all treatment conditions was performed on the data, allowing a general statement about the treatment effects on subjective appetite and food intake (34). However, one might argue that valid comparisons existed only between treatment conditions where a single variable was altered, and that an ANOVA invoNing all four treatment conditions would be unable to detect the subtle effects of any given treatment. Therefore, the following treatment pairs, where a single variable was altered, were also analyzed: A vs. B (water control vs. APM, 2 minutes); B vs. C (duration of stimulation, 2 vs. 10 minutes); C vs. D (amount of stimulus, 160 mg APM vs. 320 mg APM). Because it has been shown that responses to food vary between individuals of high and low restraint [based upon their score on the Restrained Eaters Questionnaire (9)], a secondary analysis of the data was conducted with restrained/nonrestrained as an additional main effect. Food intake and selection. Total energy (kcal) intake data were analyzed through a one-way repeated measures ANOVA (Treatment as the main effect). Macronutrient consumption was analyzed through a two-way repeated measures ANOVA (Treatment × Macronutrient), as was food choice (Treatment x Food Type). Visual analogue scales. Treatment baseline for the VAS scores was taken 5 minutes prior to consumption of the preload. The effect of treatment and time on VAS scores was calculated by subtracting the baseline VAS from the subsequent VAS scores. Thus each subject's data are expressed relative to their individual baseline values. For VAS scores of subjective appetite, the data for each question were analyzed separately by a 2-way repeated measures ANOVA, with Treatment and Time as main effects. The questions from the food appeal VAS scores were grouped by major component (protein, carbohydrate, fat, or low calorie) and then analyzed through a three-way ANOVA (Treatment × Macronutrient × Time). All post hoc comparisons were conducted using the NewmanKeuls procedure and the Studentized range statistic, q. RESULTS
Food Intake and Selection The analysis across all treatments revealed that preload had no significant effect on total caloric intake at the lunch-time meal, F(3,57)=0.29 (Fig. 1). In addition, there was no treatment order effect on food intake, F(3,57)= 1.63. Comparisons between designated treatments failed to uncover any effect due to a) aspartame-containing diet soft drink, b) duration of stimulation, or c) amount of diet soft drink consumed, on total caloric lunch-time intake [largest F(1,18)= 0.55]. Macronntrients were not consumed in equal amounts, F(2,38) = 55.0, p
0031-9384/91 $3.00 + .00
Soft Drinks With Aspartame: Effect on Subjective Hunger, Food Selection, and Food Intake of Young Adult Males RICHARD M. BLACK,*t
PHYLLIS TANAKA,*
LAWRENCE
A. L E I T E R * t
A N D G. H A R V E Y A N D E R S O N .1
*Department of Nutritional Sciences, #Department of Medicine, "~Department of Psychiatry Faculty of Medicine, University of Toronto, Toronto, Canada R e c e i v e d 15 M a y 1990 BLACK, R. M., P. TANAKA, L. A. LEITER AND G. H. ANDERSON. Soft drinks with aspartame: Effect on subjective hunger, food selection, andfood intake of young adult males. PHYSIOL BEHAV 49(4) 803-810, 1991.--Ingestion of aspartame-sweetened beverages has been reported to increase subjective measures of appetite. This study examined the effects of familiar carbonated soft drinks sweetened with aspartame on subjective hunger, energy intake and macronutrient selection at a lunch-time meal. Subjects were 20 normal weight young adult males, classified as either restrained or nonrestralned eaters. Four treatments of carbonated beverages included 280 ml of mineral water, one can of a soft drink (280 ml) consumed in either 2 or 10 minutes, or two cans of a soft drink (560 ml) consumed in 10 minutes, administered at 11:00 a.m. Subjective hunger and food appeal were measured from 9:30 a.m. to 12:30 p.m., and food intake data were obtained from a buffet lunch given at 12:00 noon. There were no treatment effects on energy intake, macronutrient selection or food choice at the lunch-time meal, or food appeal, though restrained eaters consumed more than nonrestralned eaters in all four treatment conditions. Consumption of two soft drinks (560 ml, 320 mg aspartame) significantly reduced subjective hunger from 11:05 a.m. to 11:30 a.m. compared to one soft drink (280 ml, 160 mg aspartame) or 280 ml of mineral water. Thus ingestion of soft drinks containing aspartame did not increase short-term subjective hunger or food intake. Aspartame
Subjective hunger
Human behavior
Feeding
THE nonnutritive sweetener aspartame (APM) is becoming an increasingly popular sucrose substitute in foods and beverages. However, when such high intensity sweeteners are used as replacement for nutritive sweeteners in foods and beverages, the effect on food intake is uncertain. There are various reports suggesting that such replacement may reduce (13, 25, 33), have no effect (8,15) or even enhance food intake (4, 20, 21). The possibility of enhancing food intake through consumption of nonnutritive sweeteners was raised by reports of an increase in subjective hunger following sweetener ingestion in water [e.g., (4,21)], in yoghurt (20), as the sole sweetener in unflavored gum (30) and by the correlation of nonnutritive sweetener usage with increased rate of weight gain in an epidemiological study (28). The putative mechanism for the appetite-enhancing effect of nonnutritive sweeteners has been elicitation of a cephalic response resulting from the taste of the sweetener (20,30). Cephalic responses can stimulate insulin release, increasing glucose uptake by tissue, which in turn reduces blood glucose levels and ostensibly stimulates appetite [cf. (14, 17, 18, 32)]. It has been hypothesized that, in contrast to nutritive sweeteners, nonnutritive
sweeteners elicit this cephalic response without providing energy, and so the stimulated appetite is not assuaged (20,32). In addition to increases in subjective hunger, increased food intake arising from the consumption of a food with added nonnutritive sweeteners has also been reported. One hour after ingestion of a saccharin-sweetened yoghurt preload, subjective ratings of hunger increased as did lunch-time intake and total calories consumed during the remainder of the day, compared to consumption of an unsweetened yoghurt preload (20). However, others have failed to find any effect of the addition of nonnutritive sweeteners to food on energy consumption, for example when added to a breakfast cereal (15), or pudding or jello (25). It has been suggested that this failure to observe any appetite enhancement after consuming nonnutritive sweeteners may have been due in part to the use of foods as the vehicle rather than beverages [as in the initial positive finding (4)] (26). However, both short-term (18,26) and long-term (31) studies have failed to uncover any appetite or food intake enhancement associated with consumption of nonnutritive sweeteners in flavored beverages. In the previous experimental studies involving beverage con-
1Requests for reprints should be addressed to Dr. G. H. Anderson, Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, 150 College St., Toronto, Ontario, Canada M5S 1A8.
803
804
BLACK ET AL.
sumption and the acute response on appetite and food intake, the nonnutritive sweetener has been provided as a beverage or snack, generally 30 to 60 minutes prior to presentation of a lunch-time meal. It is important to note that, without exception, these studies did not control for time since, macronutrient content of, or energy content of, the previous meal, i.e., breakfast. As such, subtle effects on appetite engendered by the nonnutritive sweetener may have been masked. Furthermore, while some have attempted to relate their f'mdings to consumption of commercially available soft drinks containing nonnutritive sweeteners such as aspartame [cf. (15, 19, 26)], no direct tests of the effects on appetite of consuming such soft drinks have been conducted. Therefore, the present study strictly controlled timing and size of the breakfast meal on test days, and delivered the nonnutritive sweetener aspartame in a commercially available soft drink, commonly referred to as a diet soft drink. We report herein the effects of both volume and duration of exposure to diet soft drinks on subjective measures of hunger and on lunch-time food intake.
TABLE 1 EXPERIMENTAL SCHEDULE Time
Procedure
10:00 p.m. (night before) 7:45 a.m. 8:00 a.m. 9:30 a.m. 10:55 a.m. 11:00 a.m.
11:05 a.m. l h l 0 a.m. 11:15 a.m. 11:20 a.m. 11:30 a.m.
METHOD 11:45 a.m.
Subjects
12:00 p.m.
Twenty male subjects [ n = 2 0 , age 19 to 25 years, Body Mass Index (BMI, weight/height 2, units are kg/m 2) 22 to 29] participated in the study. Subjects were recruited by posters placed throughout the University of Toronto and by word of mouth. Excluded from the study were those who smoked, followed a vegetarian diet, or had a diagnosis of phenylketonuria, a food allergy, a major medical illness, or received medications. The subjects gave informed consent to participate in the study, approved by the University of Toronto Human Subjects Review Committee.
12:05 p.m. 12:30 p.m.
Procedure Upon recruitment, subject weight and height were measured. Each subject also completed the Restrained Eaters Test (9), as well as a Food Liking Checklist and a Food Acceptability List, from which an individualized buffet lunch menu was prepared. Subjects also indicated a preferred soft drink flavour from a choice of Sprite, 7-UP, orange, ginger ale or cream soda, to be consumed during the study. The full experimental schedule is described in Table 1. Subjects were required to fast from 10:00 p.m. the previous night until breakfast was provided. Subjects arrived at the feeding studies laboratory in the Department of Nutritional Sciences, University of Toronto, at 7:45 a.m. Each subject was then presented with a breakfast meal (Table 2) to be entirely consumed within 30 minutes. The breakfast meal was individually tailored to each subject's weight, so that it provided 25% of the average daily caloric intake, based on tabulated estimates of average energy expenditure (e.g., 3000 kcal/day for a 71-kg man of average height and age range) (7). Breakfast calories were adjusted for an individual's weight by altering the amount of cereal and milk presented for consumption. Measures of subjective appetite and food preference were taken throughout the morning (Table 1). Four treatments were administered at 1 h 0 0 a.m., with treatment order being fully randomized across subjects (Table 3). Subjects were unaware of the nature of the soft drink, i.e., regular or diet. Soft drinks of the predetermined flavor preference for the individual were served cold (5°C) in 300-ml plastic cups. Subjects were required to consume all of the beverage provided within the time allotted. Lunch was provided at 12:05 p.m. Each subject was served an individualized buffet lunch, prepared in a visually appealing man-
Subject fasts Subject arrives at Feeding Studies Laboratory Subjects consume breakfast VAS Motivation to eat VAS Food Appeal VAS Motivation to eat VAS Food Appeal Treatment (preload) VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Motivation to eat VAS Food Appeal VAS Motivation to eat VAS Motivation to eat VAS Food Appeal Buffet lunch served VAS Motivation to eat VAS Food Appeal Beverage Consumption checklist*
*To be answered after completing final test session only. ner and served in excess, and instructed to eat until comfortably full. Subjects were allowed 30 minutes to complete their lunch. Lunch size was sufficient to ensure that no subject would consume all that was offered in total, or of any one item. While individual lunches varied in the foods that were presented, overall macronutrient content was essentially constant across lunches. For any given subject, the buffet lunch was the same at each test session. A typical lunch menu is presented in Table 4.
Dependent Variables Food intake and selection. At the end of each lunch, food consumed was measured and total calories consumed were calculated. The number of calories consumed as protein (PRO), carbohydrate (CHO) and fat (FAT) were also calculated. Macronutrient
TABLE 2 COMPOSITION OF AN AVERAGE BREAKFAST
Food
Quantity
kcal
PRO g
CHO g
FAT g
Shreddies 2% milk Oat-bananaraisin muffin Orange juice
250 ml 175 ml 2 small
209 96 330
5.1 6.4 6.0
46.1 9.3 58.0
0.4 3.7 10.0
250 ml
118
1.8
28.4
0.2
753
16.4 (8%)
141.8 (75%)
14.3 (17%)
Optional coffee was available with a maximum addition of 10 g sugar and 30 ml milk = 50 kcal.
SOFT DRINKS WITH ASPARTAME
805
TABLE 3
10-cm line word anchored at each end. Subjective appetite was assessed with the aid of four different VAS's which measured 1) desire to eat, 2) hunger, 3) fullness, and 4) prospective consumption (27). The food appeal VAS measured the appeal (no appeal at a l l . . , very appealing) of 32 commonly available foods. Portion sizes were equated for energy content. These foods were classified by principal macronutrient component (i.e., protein, carbohydrate, fat or low calorie, 8 foods per classification for a total of 32 foods) (21).
EXPERIMENTAL DESIGN AND ASPARTAME CONTENT OF SOFT DRINKS
Treatment A B C D
Aspartame (rag)*
Preload 280 ml Carbonated Water (control) 280 ml Diet Soft Drink 280 ml Diet Soft Drink 560 ml Diet Soft Drink
Consumption (rain)
0
2
160 to 170 160 to 170 320 to 340
2 10 10
*Precise amounts depended upon the diet pop consumed.
composition of the foods was determined by chemical analysis results obtained through the manufacturer when possible, and otherwise from food composition tables. Because the foods were of relatively constant composition (with the possible exception of the fat content of the beef), it was assumed that any minor errors in macronutrient composition and total energy content reported in the food tables would not contribute substantially to the within subject variability on test versus control days. Foods chosen at the lunch-time meal were placed in the following categories: bread, meat, dairy, condiment, or dessert. Calculation of the energy content of foods (kcal) consumed from each category allowed determination of any treatment effects on selection of these foods. Visual analogue scales. Measurement of subjective appetite and food appeal were made throughout the morning using visual analogue scales (VAS) (Table 1). Each VAS was a continuous
TABLE 4 TYPICAL BUFFET LUNCH MENU
Food or Beverage Bread: Whole Wheat Meat: Ham Turkey Bologna Dairy: Cheese (cheddar) Milk (whole) Orange juice Water Condiments: Butter Mayonnaise Mustard Lettuce Dessert: Chocolate chip cookies Oatmeal cookies Oreo cookies Shortbread cookies Sara Lee Pound Cake Sara Lee Chocolate Fudge Cake
Amount
324.0 g (10 slices) 101.5 g ( 5 slices) 108.8 g ( 5 slices) 217.6 g (10 slices) 232.4 g 250 ml 250 ml 250 ml 30 g 60 g 15 g 4 leaves 5 cookies 5 cookies 5 cookies 5 cookies 3 cakes (46 g each) 3 cakes (46 g each)
Data Analysis General. The primary analysis was conducted as follows. First, an ANOVA involving all treatment conditions was performed on the data, allowing a general statement about the treatment effects on subjective appetite and food intake (34). However, one might argue that valid comparisons existed only between treatment conditions where a single variable was altered, and that an ANOVA invoNing all four treatment conditions would be unable to detect the subtle effects of any given treatment. Therefore, the following treatment pairs, where a single variable was altered, were also analyzed: A vs. B (water control vs. APM, 2 minutes); B vs. C (duration of stimulation, 2 vs. 10 minutes); C vs. D (amount of stimulus, 160 mg APM vs. 320 mg APM). Because it has been shown that responses to food vary between individuals of high and low restraint [based upon their score on the Restrained Eaters Questionnaire (9)], a secondary analysis of the data was conducted with restrained/nonrestrained as an additional main effect. Food intake and selection. Total energy (kcal) intake data were analyzed through a one-way repeated measures ANOVA (Treatment as the main effect). Macronutrient consumption was analyzed through a two-way repeated measures ANOVA (Treatment × Macronutrient), as was food choice (Treatment x Food Type). Visual analogue scales. Treatment baseline for the VAS scores was taken 5 minutes prior to consumption of the preload. The effect of treatment and time on VAS scores was calculated by subtracting the baseline VAS from the subsequent VAS scores. Thus each subject's data are expressed relative to their individual baseline values. For VAS scores of subjective appetite, the data for each question were analyzed separately by a 2-way repeated measures ANOVA, with Treatment and Time as main effects. The questions from the food appeal VAS scores were grouped by major component (protein, carbohydrate, fat, or low calorie) and then analyzed through a three-way ANOVA (Treatment × Macronutrient × Time). All post hoc comparisons were conducted using the NewmanKeuls procedure and the Studentized range statistic, q. RESULTS
Food Intake and Selection The analysis across all treatments revealed that preload had no significant effect on total caloric intake at the lunch-time meal, F(3,57)=0.29 (Fig. 1). In addition, there was no treatment order effect on food intake, F(3,57)= 1.63. Comparisons between designated treatments failed to uncover any effect due to a) aspartame-containing diet soft drink, b) duration of stimulation, or c) amount of diet soft drink consumed, on total caloric lunch-time intake [largest F(1,18)= 0.55]. Macronntrients were not consumed in equal amounts, F(2,38) = 55.0, p
