NNNS: Appetite (2006)
Blackburn GL et al, The effect of aspartame as part of a multidisciplinary weight-control program on short- and long-term control of body weight, Am J Clin Nutr. 1997:65:409-18.
- Between July 1988 and August 1989, women who were obese were recuited to participate in a 17-month weight control program
- Obesity=140% to 225% of ideal body weight, based on the 1959 Metropolitan Life Insurance Tables.
- Healthy women, aged 20 to 60 years
- Alcohol intake was ≤15% of total energy
- Expected to reside in the Boston area for ≥18 months
- Willing to abstain from or to use aspartame-sweetened products for the duration of the study
- Not dieted within the last 90 days
- Were not pregnant nor were planning to become pregnant over the next 18 months.
- Depressed or revealed a tendency toward disordered eating, as determined by scores on the Beck's depression inventory and EAT-40 (>20 and ≤20, respectively)
- Phenylketonuria, hypothyroidism, active psychiatric treatment (including frank eating disorders), significant hepatic insufficiency, respiratory insufficiency, insulin-dependent diabetes and certain cardiac problems that would contraindicate the use of a low-energy diet.
- Between July 1988 and August 1989, women who were obese were recruited to participate in a 17-month weight control program.
- Participants were recruited by advertisement, physician-referral and word-of-mouth.
- The study was approved by the New England Deaconess Hospital Institutional Review Board and informed consent was obtained from each prospective subject, in writing, at their first clinic visit.
- Subjects then completed a detailed medical and dieting-weight history and underwent clinical and laboratory evaluation.
- Subjects were also given the 40-question eating attitudes test, Beck's depression inventory and other questionnaires to assess food prefences and cravings.
- At this first screening visit, prospective participants were taught how to keep a three-day food record by a research nutritionist. Three-day food records were brought in and reviewed for accuracy and completeness at the second screening visit.
- A prospective, randomized, stratified, two-arm parallel design
- 19 weeks, one year of weight maintenace, two-year follow-up
- Participants were told that the purpose of the study was to evaluate two research diets for their ability to promote weight-loss and long-term control of body weight. Participants were not blinded to their treatment assignments to permit intensive group-appropriate counseling.
- Three-week run-in diet.
- Allowed for water diuresis with hypoenergenetic diets and weaned all participants off low-energy sweeteners.
- ADA exchange list 4,180±836kJ per day (1,000±200kcal per day); 27% energy as protein, 49% as CHO and 24% as fat.
- Encouraged to take daily vitamin-mineral supplement, not to consume low-energy sweeteners and to begin walking 15 minutes per day, three days per week.
- Lasted 16 weeks and the run-in diet was consumed during this time.
- Aspartame group: Given their milk exchanges as aspartame-sweetened pudding or milk shakes. They were given an aspartame-sweetened non-carbonated beverage mix and packets of a tabletop sweetener containing aspartame and were encouraged to use other products sweetened with aspartame.
- No-aspartame group: Told to avoid products sweetened with any low-energy sweetener and to use instead up to 50g (three tsp) of sugar or honey daily as a sweetener. Participants were also given a non-energy-containing flavored seltzer water to drink, instead of diet soda and menus and recipes for low-fat low-energy foods and beverages did not include high-intensity sweeteners.
- Participants were seen weekly for 60 to 90 minutes in closed groups of 10 to 15 persons. Instructed to complete 200 minutes of aerobic exercise per week (walking), the prescribed program increased exercise levels gradually over a period of six to eight weeks.
- 12-month phase, energy intake was adjusted on an individual basis to maintain each participant's reduced body weight.
- Diets provide about 6,270±1,254kJ per day (1,500±300kcal per day): 24% of energy as fat, 56% as CHO and 20% as protein with an emphasis on restricted fat intake.
- Participants were either encouraged or discouraged from using aspartame-sweetened products according to their original assignment.
- Personal exercise program recommended by exercise physiologist.
- Participants attended an hour-long monthly group sessions led by a research nutritionist who focused on relapse prevention and strategies for maintaining weight loss.
- After the maintenance period, subjects were contacted annually for two years to determine body weight, aspartame intake, exercise level, subjective measures of eating control and intercurrent health events.
- Two-sided tests were performed throughout.
- Ststistical tests were considered significant at the P=0.05 level.
- Unpaired T-tests were used for continous measures and Fischer's exact test was used for categorical measures within treatment groups.
- Treatment group differences were evaluated by use of T-tests and linear-regression models.
- Paired T-tests, multi-regression analyses and Pearson product moment correlations were also used.
- Used SAS software.
- Aspartame intake: Measured by use of a form that listed, by food group, all foods containing aspartame at the time of the study. Recorded use over seven days. Average values for the particular food groups were used to determine mean intake of aspartame. Form administered at baseline and Weeks 19, 71 and 175.
- Body weight: Measured on the same digital spring scale (model no. 8850, Detecto Scale Co., Webb City, MO) to the nearest pound. Measured weekly during active weight loss, monthly during maintenance and annually thereafter.
- Exercise: Minutes of exercise per week were calculated from a daily exercise log kept by all participants during the week immediately before data collection (baseline and Weeks 19, 71 and 175).
- Dietary intake: Three-day food records. A research nutritionist instructed each subject on how to complete food records with the use of food models and household measures. Records sent to the Nutritional Coding Center at the University of Minnesota for coding and analysis. Food records were kept at baseline and Weeks 19, 71 and 175.
- Subjective measures (appetite): Level of hunger and desire for sweets were assessed by a self-administered questionnaire. The subject was asked to rate their level of hunger for sweets over the past seven days by use of a 10-point category scale. Ratings for hunger and desire for sweets were anchored with "none" and "severe." Subjective levels of eating control were assessed by use of a 10-point category scale that was anchored with binging and restricting. Administered at baseline and Weeks 19, 71 and 175. Self-assessment of eating control was compared with more direct measures of food intake from dietary records.
- Intercurrent health events: Were documented in the patient's chart at each clinic visit by a research nurse according to mild, moderate and severe.
- Validation of aspartame intake and exercise: Assessment forms (see text) 10 obese subjects meeting the study entry criteria were selected to participate in a validation study of the exercise and aspartame intake forms.
- 390 were screened initially. 222 subjects were not enrolled because they were not eligible or because they decided that they would be unable to make a commitment to the study protocol. The remaining 168 subjects gave written consent and entered the run-in phase. Five subjects dropped out during these three weeks.
- After stratification by initial body weight and clinic site, a total of 163 subjects were randomly assigned to a treatment group at the end of the run-in: 82 to aspartame; 81 to the no-aspartame group.
- 16% (11 in aspartame and 16 in no-aspartame) dropped out during the active weight loss phase. Reasons cited for dropping out included relocation or conflict with job schedule (N=3), inablility to comply with the program (N=10), auto accident (N=1), family or personal problems (N=3) and loss of interest (N=10). 136 completed the Week 19 visit.
- 125 (61 aspartame, 64 no-aspartame) or 77% of the original population, participated on maintenance and completed the Week 71 visit.
- 86 (41 aspartame, 45 no-aspartame) or 52% of the original population attended the two-year follow-up.
- 20 to 60 years.
Anthropometrics and Location
- After completing the baseline evaluation, eligible subjects were stratified on the basis of percentage of ideal body weight (140% to 179% and 180% to 225%) and clinic assignment (Brookline, Quincy, Wellesley, Winchester, Boston) and were randomly assigned to one of two dietary treatment programs by use of a computer-generated identification number.
- Women in both treatment groups lost about 10% of initial body weight (10kg) during active weight loss.
- Aspartame treatment group: Aspartame intake was positively correlated with percentage of weight lost during active weight loss (R=0.32; P<0.01).
- Maintenance and follow-up: The aspartame group experienced a 2.6% (2.6kg) and 4.6% (4.6kg) regain of initial body weight after Weeks 71 and 175, respectively, whereas those in the non-aspartame group gained an average of 5.4% (5.4kg) and 9.4% (9.4kg), respectively. The aspartame group lost significantly more weight overall (P=0.028) and regained significantly less during maintenance and follow-up (P=0.046) than did the non-aspartame group.
- Percentage of weight lost at Weeks 71 and 175 were positively correlated with exercise (R=0.32; P<0.001 and R=0.34; P<0.01), respectively and self-reported eating control (R=0.37; P<0.001 and R=0.33, P<0.01), respectively.
- End of active weight loss: Desire for sweets decreased significantly in both groups from baseline to the end of active treatment. Self-reported hunger did not differ from baseline in either treatment group. Eating control increased significantly in both treatment groups at Week 19.
- Week 71: No significant differences existed between the treatment groups on any of the subjective variables.
- Week 151: The eating control in the non-asparatame group converged to the same values in the aspartame group as they regained their weight.
|Aspartame (N)||Non-Aspartame (N)|
|Baseline||4.0±0.3 (82)||4.1± 0.3 (81)|
|End of AWL||4.0±0.3 (81)||4.2±0.3 (80)|
|Week 71||4.2±0.3 (51)||4.3±0.3 (50)|
|Week 175||6.0±0.4 (39)||6.6±0.3 (43)|
|Desire for Sweets|
|Baseline||5.2±0.3 (82)||5.3±0.3 (81)|
|End of AWL||4.0±0.32 (82)||4.3±0.42 (80)|
|Week 71||5.0±0.4 (52)||4.6±0.4 (50)|
|Week 175||5.3±0.4 (40)||5.4±0.4 (42)|
|Baseline||3.5±0.3 (82)||4.0±0.3 (81)|
|End of AWL||6.0±0.33 (82)||6.2±0.33 (81)|
|Week 71||4.3±0.42 (52)||4.9±0.44 (50)|
|Week 175||4.9±0.4 (40)||5.2±0.44 (43)|
1=Mean ± SEM; N in brackets. Scores are based on a scale of 0 (none) to 10 (severe); Eating control (0=bingeing, 10=restriciting)
2=Significantly different from baseline: P<0.01
3=Significantly different from baseline: P<0.0001
4=Significantly different from baseline: P<0.05.
- The results of this study showed that, whereas it was not necessary to consume aspartame to achieve medically significant weight loss, consumption of higher amounts of aspartame was associated with greater weight loss among middle-aged women who were obese, using aspartame as part of a weight-loss program.
- Participation in a multi-disciplinary weight-control program that includes aspartame and exercise was associated with better long-term control of body weight.
- This study provided evidence that a safe and cost-effective alternative to pharmacologic management exists for the long-term weight management of obesity.
- During the study, no differences were found between groups for desire for sweets or hunger, although desire for sweets decreased significantly in both groups at the end of the dietary restriction phase. The aspartame diet may have reduced the the desire for sweets by providing ample low-energy sweetness as part of the program.
- Lack of control with a free-living population. However, it provides greater applicability of results.
- Generalizability is another limitation.
- Participants were highly motivated, well educated, middle to upper-middle class white women willing to invest a great deal of time and effort in the program.
- The generalizability of these results to men and women from other socio-economic and ethnic groups is not known.
[Note (blinding): Although no attempt was made to blind the participants or researchers to the treatment group assignment, we do not believe that this decision limited the study. Prior research found that knowing whether a food was sweetened with aspartame or sugar had no influence on short-term food intake or perceived appetite; both informed and noninformed subjects responded similarly.]
|University/Hospital:||Beth Israel Deaconess Medical Center, Harvard Medical School, University of Nebraska|
- Excellent study
- Overall, no difference between the groups for weight loss; better weight maintenance for the aspartame group
- Products used: Milk products, drinks, sweeteners for one group vs. sugar, honey.
Quality Criteria Checklist: Primary Research
|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|
|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%.)||Yes|
|4.3.||Were all enrolled subjects/patients (in the original sample) accounted for?||Yes|
|4.4.||Were reasons for withdrawals similar across groups?||Yes|
|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?||No|
|5.1.||In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?||No|
|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.)||No|
|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?||Yes|
|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?||Yes|
|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)?||Yes|
|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?||Yes|
|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?||Yes|
|10.||Is bias due to study's funding or sponsorship unlikely?||N/A|
|10.1.||Were sources of funding and investigators' affiliations described?||Yes|
|10.2.||Was the study free from apparent conflict of interest?||Yes|