NNNS: Appetite (2006)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
The research purpose was to compare two volumes of lemonade sweetened with sucrose or aspartame, the same volumes of water and a condition in which no drink was consumed; to examine the effects on hunger, food intake and thirst.
  • Experiment One: Designed to examine the effect of different drinks on food intake when taken with the meal.
  • Experiment Two: In order to investigate a possible post-ingestive delayed effect of increased appetite, subjects were given the drinks as a pre-load 30 minutes before lunch.
  • Experiment Three: Subjects were given the drink 60 minutes before lunch and their ratings of hunger were tracked throughout the session.
Inclusion Criteria:
  • Non-smoking
  • Non-dieting
  • Normal weight for height (between 90% and 110% of ideal body weight), according to the Metropolitan Life Weight Tables
  • No food allergies or restrictions nor any medication
  • Screened using the Stunkard Eating Inventory (which measures cognitive restraint), the Eating Attitudes Test and the Zung Self-Rating Questionnaire (which measures depression)
  • Score of less than 10 on the Eating Inventory Test, less than 15 on the Eating Attitudes Test, less than 50 on the Zung questionnaire
  • Volunteer was required to complete a trial session in which he would rate pleasantness of foods and whether he would eat the foods (only subjects' ratings of 50 on 100mm visual analog scales were included in the experiment).
Exclusion Criteria:
Excluded if inclusion criteria listed above was not met.
Description of Study Protocol:
  • All three experiments utilized a within-subjects repeated-measures design, with each subject serving as his own control
  • Every subject received each of the following drinks:
    • Eight ounces of sucrose-sweetened lemonade
    • 16oz sucrose-sweetened lemonade
    • Eight ounces of aspartame-sweetened lemonade
    • Eight ounces of water
    • 16oz water
    • On one occasion, no drink was given.
  • Each subject was run once in each of the seven conditions and the order of presentation was counter-balanced across subjects
  • Subjects came to the laboratory at the same time for each of the seven sessions, with at least three days between sessions
  • Subjects were asked to list, upon arrival, all the foods consumed at dinner the night before the session and at breakfast the morning of the session. These food diaries were used to monitor subjects' compliance, since they had been instructed to eat a normal dinner the night before and to eat the same breakfast on the mornings of all the session days.
  • After the final session, all subjects were given a discharge questionnaire to answer.

Experiment One

  • At 12:00 p.m., subjects arrived at the laboratory at their usual time for each of the seven sessions.
  • Upon arrival, subjects completed their initial appetite ratings, which served as the baseline rating
  • Received their self-selection lunch meal along with the test drink or no drink and were instructed to eat as much as they wanted and told if they wanted more to ask for it.
  • Instructed to consume all of the drink during the meal and given a maximum of 20 min to eat.
  • A second set of appetite ratings were done after subjects had eaten as much as they wanted.
  • A third set of ratings was done after subjects had spent an hour sitting quietly in their cubicles.

Experiment Two

  • Subjects arrived at the laboratory 30 minutes before their usual lunch times
  • Upon arrival, subjects completed their initial appetite ratings.
  • Subjects received lemonade or water and were instructed to consume all of the drink
    • Subjects were given five minutes for eight ounce drinks and 10 minutes for 16oz drinks
    • In the no-load condition, subjects, after their ratings, did not receive a drink or were told to sit in their cubicles for five minutes.
  • A second set of appetite ratings was done after the subjects had finished their drink and were asked to sit in their cubicles for 30 minutes
  • Subjects then rated hunger and thirst for a third time and then were served lunch.
    • Subjects were given same instructions as in Experiment One for lunch and were allowed 20 minutes to eat
    • Subjects rated hunger, thirst, etc., immediately and then one hour after lunch.

Experiment Three

  • Subjects arrived at the laboratory 60 minutes before their usual lunch times
  • Upon arrival, subjects completed their initial hunger, thirst, fullness and other sensations
  • Subjects received lemonade, water or no drink and were instructed to consume all of the drink
    • A second set of appetite ratings was done after subjects finished their drink and had been asked to sit in their cubicles for 30 minutes
    • Subjects then rated appetite for a third time, then waited 30 minutes and completed a fourth set of ratings.
  • One hour after coming to the laboratory, subjects were given a self-selection lunch and were instructed to eat as much as they wanted
    • Subjects were allowed 20 minutes to eat as much as they wanted.
  • Subjects rated appetite immediately following and then one hour after lunch.


  • Subjects were naive as to the sweetener manipulation in the study.

Statistical Analysis

  • Energy intake including and not including the calories from the lemonade was analyzed using two-way analysis of variance with repeated-measures (BMDP software) to determine if there were any significant differences among conditions
  • Post hoc Tukey’s HSD test was done when any significant main effects were observed to ascertain which means differed significantly
  • Macronutrient selection in the different conditions was done by comparing the percentages of the total macronutrients consumed (by weight) derived from fat, carbohydrates or protein, across conditions using two-way analysis of variance
  • Appetite rating changes (hunger, thirst, fullness, desire to eat, desire to drink, prospective drinking) were analyzed using two-way three-factor analysis of variance condition (type of load), dose (eight or 16oz) and time as factors
  • Pearson’s product moment tests were used in all three experiments to determine the degree of correlation (from baseline to immediately after lunch) during each condition
  • The Greenhouse-Geisser probability value is given instead of the tail probability value, whenever statistically significant, so that Type I errors often associated with repeated measures of analysis may be minimized.
Data Collection Summary:

Timing of Measurements

  • Visual analog scales: Rated their hunger, thirst, fullness, desire to eat, desire to drink, how much they thought they could eat and how much they thought they could drink at specific times throughout the sessions by marking their responses on 100mm visual analog scales. Each subject’s baseline appetite ratings were checked at the beginning of each session to ensure that the ratings deviated no more than ±15mm across all sessions.
  • Food and macronutrients: The test drink was a lemonade made with chilled water (7ºC) and freshly squeezed lemon juice sweetened to equal intensity with either sucrose or aspartame (a ratio of 200g of sucrose for every gram of aspartame was used to match sweetness). The sweetener concentrations were comparable to the amounts found in commercially available soft drinks.
Drink Characteristics
Drink Volume Sweetener (g) Calories
Lemonade Eight ounces Sucrose (20) 83
Lemonade 16oz Sucrose (40) 166
Lemonade Eight ounces Aspartame (0.11) 5
Lemonade 16oz Aspartame (0.22) 10
Water Eight ounces None 0
Water 16oz None 0
Triangle Test

Tasters were required to choose the two samples most similar in taste from three unlabeled samples of lemonade (two samples of one type of lemonade and one sample of the other type). Order of presentation of the samples was counter-balanced. All subjects were given two triangle tests after their last session to determine how well the covert manipulation worked. 
Selection of Lunch

All foods were weighed before being served and were re-weighed after the subjects had eaten, to obtain the amount consumed (g) of each food.
Description of Actual Data Sample:
  • Initial sample: 42 healthy males
  • Age: 21 to 39 years; mean age 25.0, SD=4.3
  • Anthropometrics: 9.7%, SD=0.3% of the Metropolitan Life Weight Tables.
Summary of Results:

Results, Experiment One

  • Analysis of variance comparing energy intake during the self-selection meal across all seven conditions, without including lemonade calories, produced no statistically significant differences
  • Energy intake was not affected by subjects being deprived of a drink when eating their meal. Interestingly, when lemonade calories were added to the calories consumed during lunch, a two-factor two-way analysis of variance test comparing intake associated with the drink conditions showed a significant main effect for condition, P<0.01. Post hoc comparison of the means indicated that subjects consumed significantly more calories with the sucrose-sweetened lemonades than with the aspartame-sweetened lemonades or water P<0.01.    
Food and macronutrient selection
  • No significant differences were found in fat, carbohydrate and protein consumption, when intake was compared across conditions.
  • Analysis of variance of the difference scores for hunger, fullness, desire to eat and prospective consumption ratings (after lunch minus the baseline rating and one hour after lunch minus the baseline) sowed the main effect of condition to be non-significant
  • The difference scores for hunger exhibited a trend for dose, while prospective consumption ratings were significant for dose (P<0.05). These ratings decreased more following the 16oz drinks than following the eight-ounce drinks.
  • The main effect for time was significant for hunger and fullness. There was a significant interaction between dose and time for hunger ratings, due to lower ratings immediately after lunch in the 16oz conditions (sucrose, aspartame and water) than in the eight-ounce conditions (P<0.004).
  • The change in hunger from before to after lunch and total intake (lunch plus drink) during lunch found only the intake in the eight-ouncec water condition to be significantly correlated to the change in hunger. 
  • There was a strong effect of dose, with the 16oz drinks decreasing thirst significantly more than the eight-ounce drinks and of time.
  • Subjects were significantly less thirsty after having a drink than after not having a drink, except in the eight-ounce sucrose condition (P<0.008).
Food intake
  • Food intake in the no-load condition was not different from the drink conditions, even though the thirst ratings (except in the eight-ounce sucrose condition) were significantly different
  • No significant correlation was found between thirst changes and food intake during lunch.

Triangle test

  • Only 5 of the 14 subjects chose the correct pair of samples in their first trial. In the second trial 9 of the 14 subjects chose correctly.
Results, Experiment Two
Energy intake
  • Energy intake analysis, including the drink calories comparing all seven conditions, indicated that there were significant differences (P<0.02)
  • Post hoc comparisons revealed significantly fewer calories were consumed in the no-load condition (P<0.05) than after the 16oz sucrose-sweetened lemonade pre-load, when calories from the drinks were added. 
Macronutrient and food selection
  • Revealed no significant differences across conditions.
  • Analysis of the overall changes in hunger and appetite ratings showed no statistically significant differences for the main effects of condition and dose
  • The main effect of time was significant for all appetite ratings (P<0.001). No correlation was found between total calorie intake and hunger ratings (the change from baseline to immediately after lunch).
  • Neither comparison of the change in thirst nor the desire to drink ratings indicated differences across drink types
  • The 16oz drinks decreased thirst significantly more than the eight-ounce drinks (P<0.008)
  • The changes in desire to drink ratings and the amount the subjects thought they could drink were significant for the main effect of dose, due to the decrease in ratings associated with 16oz drinks
  • A significant dose-by-time interaction was observed for change in thirst (P<0.003), desire to drink, (P<0.001) and prospective drinking ratings (P<0.001)
  • All drink conditions, when compared to the no-load condition, decreased thirst significantly more, except for the eight-ounce sucrose- and eight-ounce aspartame-sweetened lemonades.
Triangle test
  • Nine out of 14 subjects chose the correct pair in their first trial
  • Seven out of 14 chose correctly in their second trail. 
Results, Experiment Three

Energy intake
  • Comparison of the food calories consumed at lunch in the seven conditions revealed no differences as well as when the calories from the drink were added.
Macronutrient selection
  • Subjects consumed amounts of fat, carbohydrates and protein similar to in Experiments One and Two.
  • No statistical differences were found among the seven conditions for changes in hunger and appetite ratings
  • No correlations were found between the change in hunger ratings from baseline to after lunch and total intake during the meal within each condition.
  • No statistical differences among changes in thirst, desire to drink or prospective drink ratings, when comparing drink types
  • Significant differences were found for the change in thirst, desire to drink and prospective drinking between the eight-ounce conditions and the 16oz conditions
  • The 16oz drinks decreased thirst, desire to drink and prospective drink significantly more than the eight-ounce drinks. These ratings changed significantly over time (P<0.0001).
Triangle test
  • Nine out of 14 subjects chose the correct pair in samples in Trial One; nine in Trial Two; six of the 14 subjects guessed the correct pair in both tests
  • No subject was able to guess the purpose of the experiment.
Mean Calories±SD Consumed at Lunch With and Without Drink Calories
Intake (kcal) Intake (kcal) + Drink ±SD
Experiment One: Drink with lunch      
8 oz sucrose 1,138.3 1,221.3+ 162.6
16 oz sucrose 1,045.7 1,211.7+ 303.7
8 oz aspartame 1,021.6 1,026.8 295.0
16 oz aspartame 1,113.4 1,123.8 277.3
8 oz water 1,083.2 1,083.2 336.9
16 oz water 1,077.3 1,077.3 330.1
no load 1,083.2 1,083.2 251.0
Experiment Two: Drink 30 Minutes Before Lunch      
8 oz sucrose 1,098.1 1,181.1 409.0
16 oz sucrose 1,096.4 1,262.4* 495.6
8 oz aspartame 1,092.9 1,098.1 382.7
16 oz aspartame 1,138.4 1,148.8 529.4
8 oz water 1,137.1 1,137.1 553.0
16 oz water 1,198.6 1,198.6 598.5
no load 1,053.2 1,053.2 409.9
Experiment Three: Drink 60 Minutes Before Lunch      
Eight ounces sucrose 1,104.1 1,187.1 221.7
16 oz sucrose 1,133.6 1,299.6 230.2
Eight ounces aspartame 1,211.2 1,216.4 138.9
16 oz aspartame 1,140.0 1,150.4 237.7
Eight ounces water 1,146.8 1,146.8 274.4
16oz water 1,225.2 1,225.2 250.1
No load 1,150.4 1,150.4 176.4
*P<0.05, compared with intake in the no load condition
†P<0.01, compared wth intake in aspartame and water conditions.
Author Conclusion:
  • The results indicate that in non-dieting males, asparatame in concentrations similar to those in commercially available drinks did not increase hunger ratings or food intake
  • Caloric drinks taken with lunch increased total energy intake in that meal
  • Sucrose-sweetened drinks may decrease thirst less than water or aspartame-sweetened drinks, when taken with a meal.
Funding Source:
Government: NIDDK
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes