- Click here for explanation of classification scheme.

The purpose of the study was to use the modified sham feeding technique (MSF) to test the hypothesis that women with bulimia nervosa (BN) will ingest more solution during the orosensory stimulation of MSF than women without histories of an eating disorder.

• Healthy women between the ages of 18 and 40 years with current body weight ranging from 80% to 120% ideal body weight by Metropolitan Life Insurance Tables
• No history of eating disorder or other psychiatric illness (control)
• Met criteria for bulimia nervosa as defined in DSM-IV.

None listed.

Recruitment

Women were recruited from the surrounding community, university and medical center by flyers and newspaper and Internet advertisements.

Design

• Randomized controlled trial using the sip and spit technique for taste tasting
• Prior to the experimental session, subjects were asked to rate on visual analogue scales (VASs) their perceived sweetness, liking and wanting of each of the five experimental solutions after tasting and spitting out a small sample of each
• Also prior to beginning the experimental session, subjects completed an additional series of VASs to rate their perceived hunger, desire to eat, desire to binge, desire to vomit and anxiety
• Subjects were given a one-minute training session during which they practiced the sipping-and-spitting technique using water
• Following the training session, subjects were given access to each of 15 solutions that they were instructed to sip and spit for one minute. The solutions were presented in three sets, each containing five solutions of different aspartame concentrations in distilled water, flavored with a constant concentration of cherry Kool Aid. 

Blinding Used

Subjects were blinded to the solutions. 

Intervention

• Aspartame, a low-calorie sweetener, was substituted for sucrose in the current paradigm because pilot testing using sucrose solutions with women with eating disorders suggested that their concerns about the caloric content of sucrose solutions limited their intake, despite instructions to not swallow the solutions
• Comparison groups were Kool Aid with the aspartame concentrations at zero, 0.01%, 0.03%, 0.08% and 0.28% of weight, respectively and corresponding to sweetness intensity of sucrose solutions at 0%, 2.5%, 5%, 10% and 20%. The concentrations were selected to provide approximate sweetness intensity of sucrose and where 10% approximates the sweetness of commercially available sugar-sweetened carbonated beverages.
• Within each set, the five flavored solutions (14.4 to 15.6 C) were presented in random order. 1,900ml of each solution were presented in an identical, opaque, unmarked, closed container that prevented visualization of the volume of the solution during one-minute test (two L were prepared of each solution from which 100ml were drawn off to provide samples for the taste test). Identical containers were used to collect the liquid spit out. Subjects sipped solutions through a straw and spit the oral contents out immediately into a funnel in the top of the spit container. Subjects were observed by experimenters using a Lorex four-channel closed-circuit observation system and were signaled to start and stop sipping and spitting by a doorbell tone. Signaling was performed by an observer, who monitored the time using a digital timer.
• There was a one-minute interval between presentations of solutions. Immediately after each one-minute trial, subjects used VASs to report their perceived intensities of sweetness, wanting and liking of the solution, as well as their anxiety and desire to eat, binge and vomit
• Then the subjects rinsed their mouth with a solution consisting of baking soda dissolved in distilled water (23.7g per 1,000ml distilled water)
• For VASs, separate sheets of paper were used for each time point and subjects did not have access to their previous responses. Responses were measured to the nearest millimeter using a centimeter ruler.
• The sip and spit containers were weighed before and after each one-minute trial measured to the nearest 0.1g. The grams sipped or spit was the difference in the weight of the containers before and after each trial.
• After the entire test was completed, subjects were debriefed and asked about their expectations of the experimental hypotheses, ability to comply with experimental instructions and experience of the procedure.

Statistical Analysis

• Repeated measures ANOVA was used to analyze intake and VAS measures of the perceived intensities of sweetness, liking and wanting as a function of trial (one, two or three) and aspartame concentration, using diagnostic group (BN vs. NC) as the between-group variable
• Significant treatment effects were analyzed post hoc by the Least Significant Difference (LSD) test. Differences were considered significant when p<0.05.
• Greenhouse-Geisser correction was performed on all ANOVA results to correct for dependence among observations within subjects
• T-tests were used to compare intake and VAS ratings between BN and NC subjects at each trial of each concentration
• Separate Pearson product-moment correlation coefficients were determined for the relationships among intake and perceived sweetness, liking and wanting across aspartame concentrations and across trials, within each group of subjects (BN and NC) and among individual subjects
• Separate Pearson correlation coefficients were also determined for the relationships between intake and VAS ratings of hunger, desire to eat, desire to binge, desire to vomit, anxiety obtained at baseline (prior to sipping and spitting first flavored solution), as well as clinical measures including subject age, BMI, maximum and minimum BMI, self-reported use of artificially sweetened products in the preceding month and, for BN participants, duration of the eating disorder. Because of significant group differences on several of these measures, correlation among clinical and behavioral measures were determined within each diagnostic group separately.
• VAS data were not available for one patient with BN and one control
• Full clinical data were not available for one patient with BN and information about use of artificially sweetened products  was unavailable for one participant with BN and one control. 

Timing of Measurements

• The experimental procedure was conducted over a single one-hour period in the early afternoon, three to four hours after eating a standardized breakfast (English muffin, pat of butter, 6oz apple juice; approximately 300kcal).

Dependent Variables

• Perceived sweetness, liking and wanting rated on visual analogue scales (VASs) 
• These VASs consisted of pencil-and-paper assessments including the following questions: "How much did you LIKE what you just tasted?" "How much do you WANT MORE of what you just tasted?" and "How SWEET did what you just tasted seem to you?" Beneath each question was 10cm horizontal line, anchored at either end by "Not at all" and "Extremely." Subjects were asked to indicate their answers to these questions by placing a vertical mark along the horizontal line to estimate their experiences. VASs for each solution were on a separate piece of paper. 

Independent Variables

• Normal control: Women with no history of eating disorder or other psychiatric illness
• Bulimia nervosa: As defined in DSM-IV.

Control Variables

• Age
• BMI, lifetime maximum and minimum BMI
• Self-reported use of artificial sweetened products in the preceeding month
• Duration of the eating disorder for the BN subjects. 

Initial N

• 11 healthy women with no history of eating disorder
• Thirteen women meeting criteria for BN.

Attrition (Final N)

• One patient with BN reported misunderstanding study instructions and thinking that the solutions were prepared with sucrose and not artificial sweetener. This patient sipped minimal quantities of solution and attributed this to fear of caloric absorption; her data were excluded.
• Another patient with BN reported the solutions to taste "bitter" and on further questioning endorsed extreme sensitivity to bitter tastes in, and avoidance of, artificial sweetener as well as various vegetables and other foods; this pattern is thought to be consistent with "supertaster" status and her data were also excluded from analyses
• One control participant did not comply with instructions to rinse between solutions despite being repeatedly asked to do so and her data were also excluded
• Data from 11 BN and 10 NC subjects were analyzed.

Age

• BN (24.5 years)
• NC (26.7 years).

Other Relevant Demographics

• Illness duration for BN: 9.7 years
• Eating Disorder Examination score: BN=4.07; NC=0.16 (P<0.005)
• Beck Depression Inventory total score: BN=18.5; NC=1.4 (P<0.005)
• Weekly servings gum (pieces): BN=33.05; NC=3.41 (NS)
• Weekly 12-oz servings diet drink: BN=18.67; NC=2.63 (P<0.05)
• Weekly artificial sweetener packets: BN=20; NC=3.13 (NS)

Anthropometrics

• BMI: BN=22.46; NC=21.01 (NS)
• Weight suppression (pounds): BN=45.25; NC=16.7 (P<0.005).

 

 

 

Baseline VAS Ratings of Subjects (Mean ± SE)

Subject Group	Hunger (cm)	Desire to Eat	Desire to Binge	Desire to Vomit	Anxiety
BN	5.61 (0.45)	5.87 (0.49)	2.25 (0.99)	1.17 (0.85)	4.56 (0.89)*
NC	5.40 (0.62)	5.79 (0.61)	0.21 (0.05)	0.19 (0.06)	1.16 (0.55)

 ^*Significantly higher, P=0.006.

 Other Findings

• The major result of the study is that BN participants ingested significantly more of the solutions than NC subjects during MSF [F(1.19)=5.23, P=0.34].
• Intake in MSF was also a function of sweetener concentration [F(2.98, 56.69)=7.38, P<0.001]. Post-hoc analysis revealed that the significant effect of concentration was attributable to differences between the unsweetened solution and all other solutions and between solutions two and four (P<0.05). Intake averaged across the three trials for BN subjects was significantly larger than the intake of NC at each solution (aspartame concentration; P<0.05) except for the 0.03% aspartame solution, in which the larger intake of BN subjects was not quite significant (P=0.054).
• Sweetness was not necessary for the larger intake in BN because they also ingested significantly more of the unsweetened solution (0%) than NC (P<0.05). No significant effects of trial or of concentration were found.
• BN subjects were more likely to swallow solutions than control subjects though as with the NC the total amount was so small as to be unlikely to produce significant post-ingestive feedback. The total amount in grams swallowed by BN and NC was not significantly different.
• There was no significant difference between the ingestive responses of BN and NC to increasing concentrations of aspartame
•  Changes in aspartame concentration significantly affected intake VAS reports of liking, wanting and perceived sweetness of solutions per repeated measures ANOVA. There were no significant effects of diagnostic group or interactive effects between aspartame concentration and diagnostic group on these measures.
• The modal solution that elicited maximal liking ratings among patients with BN was the 0.28% aspartame solution. Among NC it was the 0.08% aspartame solution.
• The solution that elicited maximal wanting ratings among the majority of subjects with BN was the 0.28% aspartame solution and for the NC subjects it was spread over the range of solutions.
• The 0.28% aspartame solution elicited maximal sweetness ratings in all subjects with the exception of three patients with BN who provided maximal sweetness ratings for the 0.08% aspartame solution
• Significant correlations were found among intake and liking, wanting and sweetness among BN subjects and the associations were less robust among NC subjects
• Baseline VAS measures of anxiety were higher among patients with BN than controls and there was a trend towards higher baseline ratings of desire to binge among BN subjects compared with controls. 

These results support the feasibility of a MSF procedure using artifically sweetened solutions, and the hypothesis that the orosensory stimulation of MSF provokes larger intake in women with BN than controls.

Limitations as cited by authors:

• The scale of BN is different than the scale of controls due to different experiences in the food world. Use of labeled magnitude scaling in place of visual analogue scales would improve the validity of these measures, as would routine assessment of taster status.
• Limited range of sweetness concentrations
• Incomplete understanding on the part of subjects of the concepts of liking and wanting and difficulty in providing accurate self-assessments of these subjective states
• Small sample size.

Government:

NIMH

• This study has aspects that are not clearly written and are difficult to follow
• For example, in the methods the authors do not clearly define what baseline is (it is implied) but then talk about baseline in the discussion. Another issue of writing is the continual switching back and forth among subjects, participants and patients.
• In this reviewer's opinion, the description of statistical analyses is not clear in places
• The description of the modified sham feeding technique is not clear in places and this includes the following:
  • The experimental procedure was conducted after a standardized breakfast which was 300kcal. This consisted of an English muffin, pat of butter, 6oz apple juice. There are no results or discussion on the compliance of eating this breakfast or where the breakfast was served. Several BN subjects did not adequately perform the experimental procedure with the aspartame solutions due to concerns of caloric absorption. This raises a question about consumption of the breakfast and the resulting impact on study results.
  • Prior to the experimental session, subjects were asked to rate on VASs their perceived sweetness, liking and wanting of each of the five experimental solutions after tasting and spitting out a small sample of each. It is implied that is the baseline measure, but justification for it is not given. The way the methods section is written, this occurred before a training session on the sipping and spitting technique using water. So the importance of this is unclear as it did not appear to be different from the experimental session.
• Unlike the previous study with women with no eating disorders, the experimental session had the subjects sipping and spitting for one minute vs. two minutes used in the previous study. No justification is given for the change in procedure, thus making a generalized comparison to the results from the previous study somewhat difficult.
• The methods section talks about three sets of solutions being administered while in the discussion they are talked about as three trials. It is indicated that there was a one-minute interval between presentations of solutions. Then immediately after each one-minute trial subjects performed their ratings and rinsed their mouth out. The timing of the whole experimental session is unclear. The length of time between sets or trials is also unclear. Also, procedurally it seems that subjects would have a difficult time filling out seven VASs and rinsing their mouth out in one minute. This raises a question in this reviewer's mind about the validity and accuracy of the procedure.