- Click here for explanation of classification scheme.

The study was designed to assess, in a prospective randomized fashion, whether the high-intensity sweetener aspartame could facilitate weight loss and aid in the long-term control of body weight in an outpatient population of women who are obese.

Subjects invited to be screened met the following conditions:

• 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.
• Sedentary
• 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.

Recruitment

• 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. 

Design

• A prospective, randomized, stratified, two-arm parallel design
• 19 weeks, one year of weight maintenace, two-year follow-up

Blinding Used

• 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.

Intervention: Run-In Period

• 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.

Intervention Period

• 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. 

Mainentenance Period

• 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.

Follow-Up Period

• 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.

Statistical Analysis

• 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.

Initial N

• 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.

Attrition

• 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.

Age

• 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.

Subjective Measures

• 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.

Subjective Measures at Baseline, End of Active Weight Loss (AWL) and Weeks 71 and 75¹ 

	Aspartame (N)	Non-Aspartame (N)
Hunger
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)
Eating Control
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.
  

Limitations

• 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.]

Industry:	NutraSweet Company Food Company: Other:
University/Hospital:	Beth Israel Deaconess Medical Center, Harvard Medical School, University of Nebraska
Not-for-profit	0 Foundation associated with industry:

• 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.