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1479-5868-1-12.fm

International Journal of Behavioral
Nutrition and Physical Activity
Research
Who will lose weight? A reexamination of predictors of weight loss
in women
Pedro J Teixeira*, António L Palmeira, Teresa L Branco, Sandra S Martins,
Cláudia S Minderico, José T Barata, Analiza M Silva and Luís B Sardinha
Address: Department of Exercise and Health, Faculty of Human Movement – Technical University of Lisbon, Cruz Quebrada, PORTUGAL Email: Pedro J Teixeira* - [email protected]; António L Palmeira - [email protected]; Teresa L Branco - [email protected]; Sandra S Martins - [email protected]; Cláudia S Minderico - [email protected]; José T Barata - [email protected]; Analiza M Silva - [email protected]; Luís B Sardinha - [email protected] * Corresponding author Published: 02 August 2004 Received: 18 March 2004Accepted: 02 August 2004 International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
2004 Teixeira et al; licensee BioMed Central Ltd. This is an open-access article distributed under the terms of the Creative Commons Attribution License (which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: The purpose of this study was to analyze pretreatment predictors of short-term weight
loss in Portuguese overweight and obese women involved in a weight management program. Behavioral
and psychosocial predictors were selected a priori from previous results reported in American women
who participated in a similar program.
Methods: Subjects were 140 healthy overweight/obese women (age, 38.3 ± 5.9 y; BMI, 30.3 ± 3.7 kg/m2)
who participated in a 4-month lifestyle weight loss program consisting of group-based behavior therapy to
improve diet and increase physical activity. At baseline, all women completed a comprehensive behavioral
and psychosocial battery, in standardized conditions.
Results: Of all starting participants, 3.5% (5 subjects) did not finish the program. By treatment's end, more
than half of all women had met the recomended weight loss goals, despite a large variability in individual
results (range for weight loss = 19 kg). In bivariate and multivariate correlation/regression analysis fewer
previous diets and weight outcome evaluations, and to a lesser extent self-motivation and body image were
significant and independent predictors of weight reduction, before and after adjustment for baseline
weight. A negative and slightly curvilinear relationship best described the association between outcome
evaluations and weight change, revealing that persons with very accepting evaluations (that would accept
or be happy with minimal weight change) lost the least amount of weight while positive but moderate
evaluations of outcomes (i.e., neither low nor extremely demanding) were more predictive of success.
Among those subjects who reported having initiated more than 3–4 diets in the year before the study,
very few were found to be in the most successful group after treatment. Quality of life, self-esteem, and
exercise variables did not predict outcomes.
Conclusions: Several variables were confirmed as predictors of success in short-term weight loss and
can be used in future hypothesis-testing studies and as a part of more evolved prediction models. Previous
dieting, and pretreatment self-motivation and body image are associated with subsequent weight loss, in
agreement with earlier findings in previous samples. Weight outcome evaluations appear to display a more
complex relationship with treatment results and culture-specific factors may be useful in explaining this
pattern of association.
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its and relationship with food) could have an Predicting weight loss outcomes from information col- impact on how individuals respond to obesity therapies lected from subjects before they start weight management and also inform researchers about the role of pretreatment programs is a long-standing goal ]. In effect, if individ- variables (moderators) in treatment success. It should be ual variability in obesity treatment remains as high as it is noted that this study was not designed to evaluate the presently, identifying variables that moderate outcomes overall effectiveness of the weight loss program but to (i.e., that explain for whom treatment works and under analyze predictors of short-term results among partici- what conditions) will justifiably continue to deserve pants who displayed highly variable levels of success.
attention from researchers date, however, evi-dence shows that individual weight change cannot be accurately predicted, with only a few variables showing positive reeless, advances in theoretical Subjects were recruited from the community for a 2-year formulations regarding the process of weight cont weight management program through newspaper ads, a improved research methodologie and an increasing website, email messages on listservs, and announcement number of variables tested as potential predictors [ flyers. Subjects were required to be older than 24 years, be gest further progress is possible.
premenopausal and not currently pregnant, have a BMIhigher than 24.9 kg/m2, and be free from major disease to Among the most valuable applications of valid weight be eligible for the study. After several orientation sessions, loss prediction models is the early identification of indi- 152 women signed up for the program. During the run-in viduals with the least estimated probability of success in a phase, four women decided not to participate (reporting given treatment, who could (and perhaps should) be new time and scheduling conflicts), four did not comply directed to alternative therapies. Research specifically with testing requirements and were excluded, three aimed at studying these overweight/obese persons, who women found out they were pregnant or decided to are more resistant to current forms of treatment, would be attempt pregnancy and were also excluded, and one sub- particularly relevant. Equally important are improve- ject was found ineligible due to medical reasons ments in the matching between treatments and partici- (untreated hyperthyroidism), leaving a total of 140 pants, which are dependent on the measurement of women who started the intervention. An initial visit with relevant pretreatment variables (i.e., that are found to pre- the study physician ensured that subjects met all medical dict success). More individualized programs have the inclusion criteria. All participants agreed to refrain from potential for higher cost-effectiveness and improved over- participating in any other weight loss program and gave all success rates, by targeting specific areas of concern in written informed consent prior to participation in the selected participants or homogeneous groups [ study. The Faculty of Human Movement's Human Sub- the development of a valid and comprehensive weight jects Institutional Review Board approved the study.
loss readiness questionnaire and its use as a screening toolin obesity treatment are additional foreseeable outcomes Weight was measured twice, to the nearest 0.1 kg (averagewas used) using an electronic scale (SECA model 770, We have previously tested a large number of psychosocial Hamburg, Germany) and height was also measured twice, and behavioral variables as predictors of short-term to the nearest 0.1 cm (average was used). Body mass index weight outber of significant pretreat- (BMI) in kilograms per squared meter was calculated from ment correlates of 4-month weight loss were identified, weight (kg) and height (m). In addition to weight and including previous dieting and recent weight changes, other morphological and physiological variables assessed, self-motivation, weight outcome evaluations, body size subjects filled out a large psychosocial questionnaire bat- dissatisfaction, weight-related quality of life, self-esteem, tery prior to the first weekly treatment session. This was and exercise self-efficacy and perceived barriers. Because conducted in standardized conditions of comfort and this earlier study was primarily hypothesis-generating, silence, with a study technician attending every assess- confirmatory results are needed. The goal of the present ment period. To ensure optimal levels of concentration study was to re-evaluate the predictive value of several of and avoid overburden caused by long periods of psycho- these variables in a different sample of women who metric testing, subjects were required to attend three ses- underwent a comparable weight reduction program.
sions, each lasting approximately 45 minutes.
While our previous work has studied women in theUnited States (US), the present analysis reports on a group Portuguese versions of the Impact of Weight on Quality of of similarly-overweight/obese Portuguese females. Cross- Life – Lite (IWQOL-Llf-Motivation Inventory cultural differences in social norms regarding ideal Rosenberg's Self-esteem/Self-concept (RSE, weights, in the role of physical activity, and in eating hab- , Exercise Perceived Barriers (E), and Exercise (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
Self-efficacy (E) questionnaires were used. Details of the original English versions of these instruments are Subjects attended 15 treatment sessions in groups of 32 to described else In brief, the IWQOL-Lite meas- 35 women, for approximately 4 months. Average attend- ures weight-specific perceived quality of life on five ance to the treatment sessions was 83%. Sessions lasted dimensions of daily life (physical functioning, self- 120 minutes and included educational content and prac- esteem, sexual life, public distress, and work) and it also tical application classroom exercises in the areas of physi- provides a summary score, which was used in this study.
cal activity and exercise, diet and eating behavior, and The SMI evaluates a general (i.e., context-unspecific) ten- behavior modificationysical activity topics dency to persevere, finish tasks initiated, maintain self- included learning the energy cost associated with typical discipline, and motivate oneself. The RSE measures a per- activities, increasing daily walking and lifestyle physical son's self-respect and positive self-opinion. The EPB activity, planning and implementing a structured exercise assesses the extent to which the elements of time, effort, plan, setting appropriate goals, using logs and the pedom- and other obstacles are perceived barriers to habitual eter for self-monitoring, and choosing the right type of physical activity. The ESE measures an individual's belief exercise, among many others. Examples of covered nutri- or conviction that she can "stick with" an exercise pro- tion topics are the caloric, fat, and fiber content, and the gram for at least 6 months under varying circumstances, in energy density of common foods, the role of breakfast and the dimensions of making time for exercise and resisting meal frequency for weight control, reducing portion size, relapse. Summary scores for both the EPB and ESE were strategies to reduce the diet's fat content, preventing binge calculated and used in this study. For all instruments, and emotional eating, planning for special occasions, and higher scores indicate higher values for the constructs reducing hunger by increasing meal satiety (e.g., increas- being measured. Forward and backward translations ing fiber content). Cognitive and behavior skills like self- between English and Portuguese were performed for all monitoring, self-efficacy enhancement, dealing with questionnaires cited above. Two bilingual Portuguese lapses and relapses, enhancing body image, using contin- researchers subsequently reviewed the translated Portu- gency management strategies, and eliciting social support guese versions and minor adjustments were made to were also part of the curriculum. The intervention team improve grammar and readability. In this study, Cron- included two Ph.D.- and six M.S.-level exercise physiolo- bach's alpha estimates were as follows, for the IWQOL- gists and dietitians, and one behavioral psychologist. Sub- Lite (0.95, 31 items), SMI (0.88, 40 items), RSE (0.81, 10 jects were instructed and motivated to make small but items), EPB (0.71, 11 items), and ESE (0.77, 10 items), enduring reductions in caloric intake and to increase ensuring acceptable to high internal consistency.
energy expenditure to induce a daily energy deficit ofapproximately 300 kcal. Although weight was monitored Number of previous diets and weight history variables weekly, subjects were advised that long-term (i.e., after 1– were taken from a diet/weight history questionnaire 2 years), not necessarily rapid weight reduction was the developed specifically for this study. Weight outcome primary target. In the first session, participants were evaluations were assessed by 4 questions derived from the informed that reaching a minimum of 5% weight loss at Goals and Relative Weights Questionnaire (GRWQ, 6 months was an appropriate goal in this program and Subjects were asked to indicate their "dream" weight, and were subsequently instructed to individually calculate the also what would be their "happy", "acceptable", and "dis- number of kg that corresponded to.
appointing" weights by the end of the 4-month interven-tion. Each outcome evaluation was computed as the percentage of pretreatment measured weight. Body size Measures of central tendency, distribution, and normality dissatisfaction was assessed by the difference between self were examined for all psychosocial variables at baseline and ideal body figures selected from a list of 9 female sil- and for weight at baseline and 4 months. Following inten- houettes of incr. High scores (i.e., larger tion-to-treat principles and to include psychosocial data disparity between self and ideal figure) indicate greater from all starting subjects in statistical analysis, the Last body size dissatisfaction. For multiple-item question- Observation Carried Forward (LOCF) method was used naires, if a subject failed to correctly fill out at least 75% for 5 subjects who dropped from the program and could of all items in a summary/global scale or at least 50% of not be reached for testing at 4 months (the five subjects items in a subscale, the corresponding score was not cal- dropped after sessions number 10, 11, 12 [two subjects], culated. However, this did not automatically eliminate a and 14); in these cases, the last measured weight, which subject from analyses, if other (valid) scores could be used was assessed weekly for each woman with the same scale for the same participant.
as used in laboratory testing, was entered as their finalweight. The limitations of this method notwithstandingvariations of the LOCF are commonly used in obes-ity longitudinal trials he very small number (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
of subjects for whom 4-month weight data were imputed, using the Statistical Package for the Social Sciences (SPSS), all of which were derived from weights measured late in version 12.0.
the program, should result in relatively unbiased results[thermore, since a trend toward weight regain is common upon subjects leaving treatment, assuming no Weight loss data reported in the present study refer to the further weight change after dropping out works against initial 4 months of a longer trial. After the 4-month phase, the study's primary hypotheses, providing additional pro- subjects were randomly assigned to three distinct long- tection from type I error. One subject was removed from term intervenshows individual weight analyses that included weight outcome evaluation varia- changes for all 140 participants who started the program.
bles since her values were markedly lower than values Attrition was very low (3.5%) and average weight change from the rest of the group (i.e., it was considered a data was -2.9 ± 3.2 kg (-3.0 ± 3.2 kg, if only the 135 completers are considered). The range for weight change was about19 kg, a (large) level of individual variability providing an Rank-order correlation (Spearman's ρ) was used to esti- optimal setting to study correlates of weight loss. About mate the linear relationship between predictors and 53% of participants lost more than 3.3% of their initial weight change. All but one among independent variables weight (roughly the equivalent of a 5% weight loss after 6 assessed at baseline displayed a non-normal distribution, months, in red in Figure thus generally meeting or sur- warranting the use of this non-parametric technique. The passing the recommended weight loss goals. Eighteen per- dependent measure was expressed as the difference cent of all women (in grey in Figudid not lose, or between baseline and 4-month weight. An alternative way gained weight after 4 months.
to express weight results is to calculate the "residualized"value for 4-month weight, after the effect of baseline hows descriptive statistics for the independent weight is removed (i.e., regressed out in linear regression).
variables and their association with weight change. Fewer This method protects against overcorrection of the post by previous diets, weight outcome evaluations, and to a the pre score when using a subtraction score, and also lesser degree self-motivation and body image were posi- effectively and completely adjusts this new "change" score tively associated with weight loss. When the significance for the pretreatment we. This variable was level was adjusted for the number of variables being tested also used as a dependent variable in analyses.
(Bonferroni adjustment, new significance set at 0.005),the number of previous diets and weight outcome evalua- Quadratic terms were produced for the two weight out- tions remained significantly correlated with weight come evaluation variables, to assess the curvilinear rela- results. An additional weight history question, asking tionship between these measures and actual weight whether subjects had lost at least 5 kg in the previous 2 results. Multiple regression analysis was performed to years, was not associated with weight loss at 4 months (t assess the multivariate relationships between the inde- = 0.71, p = 0.480, comparing subjects responding "yes" pendent variables and weight change. In this regression and "no"). Two additional variables from the GRWQ were model, the selected predictors (variables which were sig- also analyzed. "Dream" weight (mean ± SD, 98.1 ± 3.9%) nificant or approached significance in the bivariate analy- was unrelated to baseline-adjusted weight loss (ρ = 0.001, sis) were forced into the model and the squared semi- p = 0.98) while "disappointing" weight outcome (77.4 ± partial correlation coefficient was calculated to quantify 7.8% of initial weight) was associated with baseline- the unique contribution of each predictor to the variance adjusted weight loss (ρ = 0.27, p = 0.002). Time at current in the dependent measur Considering the relatively weight, obesity-specific quality of life, self-esteem, and small subject-parameter ratio (24:1) and in the absence of exercise variables were not associated with weight results, strong theoretical support for a hierarchical entering of before or after adjusting for baseline weight. Significant predictors into the model, this a priori (forced) model is predictors in the bivariate analysre entered preferable to a stepwise model as it minimizes instability into a multivariate regression model to predict weight in the selection of variables into the model (and in param- change. Since "happy" and "acceptable" outcome evalua- eter estimation) caused by potential sampling biases tions were highly intercorrelated and represent similar A distribution-based criterion was employed to form three constructs, they were averaged into a single variable for equally numbered groups, split by the two tertiles of this analysis. All variables entered in the model explained weight change. Means of independent variables for the independent shares of the variance in weight loss, before three subgroups were compared by analysis of variance (not shown) and after the inclusion of baseline weight (ANOVA), followed by post-hoc comparisons (Tukey's ). Each predictor caused a significant increase in Honestly Significant Difference test). Type I error was set the model's R2 with weight outcome evaluations explain- at 0.05 for all tests. Statistical analyses were completed ing the single largest share of the dependent variable. The (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
Individual Subjects t Change After 4 Months Individual Weight Change After 4 Months. Red bars indicate subjects who lost more than 3.3% of their initial weight;
grey bars indicate subjects who did not lose weight or who gained weight.
Table 1: Correlation Between Pretreatment Variables and Weight Change at 4 Months
Number of diets in past year Months at current weight "Acceptable" weight loss (% initial) "Happy" weight loss (% initial) Impact of weight on quality of life Body size dissatisfaction Exercise perceived barriers Exercise self-efficacy Higher scores indicate higher value for characteristic tested (e.g. higher quality of life, higher self-motivation, higher body size dissatisfaction, more perceived barriers, etc.); Since weight change was coded as baseline weight subtracted to 4-month weight, weight loss is represented by a negative value (thus, a negative correlation coefficient indicates a positive correlation with weight loss). 1Four-month weight adjusted for baseline weight.
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Table 2: Multiple Regression Analysis for 4-month Changes in Weight
Squared semi-partial correlation (%) Number of diets in past year Weight outcome evaluations1 Body size dissatisfaction R2(×100) = 24.0 (adjusted R2(×100) = 20.5), SEE = 2.80 kg, F(df,123) = 7.84 (p < 0.001); 1Average of "happy" and "acceptable" weight outcome evaluations.
y = 271.3 – 6.46x + 0.038x2 change for x = 0.06 (p=0.004) Weight Outcome Evaluations (% of Initial Weight) Between Weight Outcome Evaluations and Weight Loss Relationship Between Weight Outcome Evaluations and Weight Loss. Dashed line shows curvilinear (quadratic
term) and solid line shows linear relationship between weight outcomes evaluations (average of "happy" and "acceptable" val-
ues) and weight loss (% of initial). Regression equation includes both linear and quadratic terms and R2 change refers to the
addition of the quadratic term into the model, after the linear term was already in the model.
model accounted for about 24% of the variance in 4- centage of initial weight), the more weight was later lost month weight change.
(and vice-versa, i.e., the more accepting the evaluation offuture weight loss, the less weight subjects lost). However, Weight outcome evaluations were computed as a percent- a visual inspection of these associations suggested that age of participants' initial weight. Thus, the lower this participants on the lower end of the outcome evaluation percentage, the more stringent (i.e., more demanding) distribution might not be following the overall group was a subject's evaluation of her results, and vice-versa.
trend. In fact, an additional analysis revealed that, for the We found significant and positive linear relationships whole group, a curvilinear pattern of association between outcome evaluations and weight described the relationship slightly better than a linear pat- anndicating that the more demanding the evalua- tern, for both "happy" and "acceptable" outcome evalua- tions of outcomes were at baseline (i.e., the lower the per- tions and for the average of the two variables (Figur.
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Quadratic (squared) terms were tested in regression mod- variables related to weight history (time at current weight els, following procedures described by Cohen and Cohen and large recent weight losses), were not confirmed in the [ere shown to produce small but significant present study.
increases in R2, in addition to the non-transformed, linearvariables alone. Both linear and curvilinear relationships To date, the majority of research on the treatment of over- are depicted in Figure nt for skewness in the weight and obesity has focused on assessing overall treat- weight outcomes data, regression analyses were repeated ment efficacy (expressed as mean group weight change, with the top and bottom 5% of observed values removed number of individuals reaching some marker of success, from analysis, yielding very similar results (y = 503.9 - etc.) and analyzing which programs work best, typically 11.5x + 0.065 x2; R2 change for x2 = 0.05, p = 0.010).
using randomly-assigned experimental treatment groupsrast, much less research has been under- To further explore the association of the selected predic- taken to investigate the mechanisms (mediating variables) tors with weight outcomes, subjects were divided into by which treatments affect subjects, and for whom treat- three groups based on tertiles of weight reduction ments are most effective (i.e., individual moderators). The adjusted for initial weight, and baseline psychosocial potential benefits of studying moderators and mediators measures were compared among groups. Significant over- of outcomes within the behavioral and social sciences, all (ANOVA) differences emerged for the number of pre- including for physical activity, diet, and weight control are vious diets and self-motivation, with post-hoc well described in the literature e identification comparisons showing significant mean differences only of such variables open the way to a new generation of between the most and least successful groups (Figur interventions, characterized by a higher level of individu- Considering the slightly curvilinear relationships alization and overall efficacy, both by targeting those indi- observed for the GRWQ variables, it was not surprising viduals more likely to succeed and through an increased that significant differences were not detected between focus on those mediators (treatment-related, environ- success groups for "happy" (p = 0.284) and "acceptable" mental, and individual factors, and critical interactions (p = 0.145) weight loss evaluations. Body size dissatisfac- among them) more clearly associated with ou].
tion scores were also not different among the three groups Nevertheless, empirically-derived hypotheses for the role (p = 0.43 the frequency of previous diets of moderators and mediators in the treatment of obesity reported by each success group in more detail. Of all sub- remain scant, particularly for psychosocial variables. As a jects reporting no diets initiated in the previous year, only contrasting example, sufficient evidence was already avail- 17% finished in the least successful groups. Conversely, of able in the alcohol prevention field in the early 1990's for the 20 subjects reporting 3 or more recent diets, only 3 a large multi-center trial to be funded and carried out, (15%) finished within the most successful group. Ten aimed at testing the interaction between treatment women reported having initiated 4 to 8 diets in the modality and a considerable number of individual predic- previous year, none of whom finished the 4-month pro- tors/moderators such as cognitive impairment, concep- gram in the group of women losing the most weight.
tual level, motivation, social support, and patient Discussion
This study aimed at reexamining the association between
In the present study and in other trialsprevious several pretreatment individual characteristics and success dieting and weight loss attempts have emerged as reliable in short-term behavioral weight reduction, in overweight negative predictors of weight loss. One explanation is that and moderately obese women. Ten variables which had the subset of women reporting more frequent dieting con- previously been shown to predict we tains a disproportionally high number of individuals who analyzed in a separate sample, using a comparable are, for some reason, more resistant to weight control.
research methodology. Previous dieting, self-motivation, Despite evidence showing that many individuals are suc- and body image showed significant effects as predictors cessful even after many previous failed attempts ], and in the expected direction of relationship. Participants' it is possible that some subjects in research-based obesity evaluations about possible weight outcomes were also treatment programs see those programs as just one more significantly associated with weight loss in the present among many solutions they have tried and failed at study, although in a direction opposite than what was before, and thus are more prone to low self-confidence hypothesized; more stringent evaluations of outcomes and impaired motivation. Frequent restriction of eating, had predicted worse outcomes in US wo implied in the question "how many diets have you reverse was observed in Portuguese women for whom started.?", could also be a marker for more extreme diet- more accepting attitudes towards weight loss were associ- ing behaviors that may not be sustainable after the initial ated with smaller weight changes. Earlier results for exer- boost of moalso increase the cise, quality of life, self-esteem, and also for some probability for weight rebound. More studies are needed (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
Number of Previous Diets
F=4.77 (p=0.010) F=4.03 (p=0.020) Comparison of Success Groups for Previous Dieting and Pretreatment Self-motivation Comparison of Success Groups for Previous Dieting and Pretreatment Self-motivation. Groups based on tertiles
for 4-month weight loss. F for ANOVA. Error bars show 95th confidence interval. Different letters indicate significant group
differences in post-hoc analysis (p < 0.05).
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Table 3: Frequency of Diets Initiated in the Previous Year, by Weight Loss Success Group1
Most Successful Least Successful 1Groups defined based on tertiles of 4-month weight loss adjusted for baseline weight.
to investigate the mechanisms through which previous est weight outcome evaluations were less likely to lose dieting affects weight control, a consisting finding in the weight, while in US women the opposite was observed, literature. The present report also provides indication that that is, more stringent (demanding) evaluations of possi- a threshold may exist (3–4 number of diets in the previ- ble results were predictive of poorer results. Evidence for a ous year) which is associated with a marked reduction in significant effect of outcome expectancies on weight con- the likelihood of success.
trol is extremely relevant in the context of realistic versusunrealistic expectations for weight loss [].
Four earlier reports have examined the role of self-motiva- Excessively optimistic expectations are common in US tion as a predictor of weight lohile one treatment-seeking obesehom a great additional study used a general self-efficacy questionnaire value is typically placed on reaching desired weights].
worded similarly to the SMI . The related construct of By contrast, Portuguese women, perhaps because their are autonomy-oriented motivation (defined as a motivation comparatively less exposed to external pressures to be thin style more related to a persons' own interests and values and/or because they belong to a culture where optimism and less controlled by external events) has also been eval- is less valued than in the US, were less likely to produce uated as a predic. With one exception very demanding weight-related evaluations. Accordingly, dence has supported the notion that high pretreatment we have recently reported that Portuguese women do, on levels of self-motivation and an autonomy-oriented moti- average, state overall less stringent evaluations of weight vation are beneficial traits for subsequent weight loss. The loss outcomes at baseline than their American counter- SMI has also been shown to correlate with eating variables ing the case, one hypothesis for the during weigo predict exercise behavior divergent associations for US and Portuguese samples is [trary to earlier observations in US women that, when a broad population is considered, the expecta- [rcise-related variables did not predict weight tions-outcomes relationship is indeed curvilinear (with loss in the present analysis. That is, while the more general an yet-undetermined nadir or interval representing the personality attributes related to motivation and efficacy more favorable goals/expectations) and that Portuguese were stable predictors of outcomes in weight loss across women predominantly fall on the right (more conserva- studies, the moderating role of exercise self-efficacy and tive) side of the distribution while US subjects better rep- exercise perceived barriers (time, effort, etc.) did not trans- resent the left side (more stringent).
late well from the US to the Portuguese data set. Cross-national differences such as distinct levels of social aware- In the present study, it appeared that the weights partici- ness for exercise or differences in level of knowledge, past pants would find acceptable/happy were associated with adoption levels, and/or perceived competence regarding weight loss (i.e., more "optimistic" outcome evaluations, exercise and physical activities, all of which may have more weight loss) until a certain threshold was reached, influenced answers to the exercise questionnaires, are pos- somewhere around 85 to 90% of initial weight (10–15% sible explanations for these differences.
weight loss); for women reporting outcome evaluationsbelow that level no further benefit was apparent. One pre- This study is among only a few that have analyzed associ- vious study has shown that women with more modest ations between the Goals and Relative Weights Question- absolute weight loss goals were more likely to achieve naire and subsequent weight loss. Interestingly, marked their goals, and that those who achieved their weight goals differences emerged between the present and two previ- had better weight maintenance after 2.5 years; however, ous analysesortuguese women with more mod- desired weight loss did not directly predict actual weight (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
lositive expectations expressed as a higher 0.042), the number of previous diets (ρ = 0.22, p = 0.013), reported likelihood of reaching goal weight predicted and weight-related quality of life (ρ = -0.37, p < 0.001).
larger short-term weight loss in subjects who showed Rapid and concurrent improvements in body image and lower level of fantasizing and daydreaming about benefi- eating behavior (e.g., reduction in binge episodes) have cial consequences of large wer studies been observed after surgery-induced thinnirly have shown larger weight loss goals to positively predict suggesting a close link between attitudes towards one's weight loss [ and in one other case goals had small body and weight control behaviors. Body image therapy prively, previous results and has also been shown to reduce concern with food, in the those we now report suggest that positive and moderate context of a behavioral weight control tria. Despite expectations/outcome evaluations foretell the best overall the sound theoretical rationale and supportive body of results, particularly if accompanied by a high sense of self- evidence, a note of caution must be made regarding the multidimensionality of the body image consand the proliferation of assessment instruments for body It should be noted that variables originating from the image. Although they are typically intercorrelated], GRWQ are closely related but are not equivalent to the different body image scales should be interpreted sepa- construct of outcome expectancies (the belief that certain rately as they may result in different patterns of associa- actions will lead to the proj) or to weight loss goals. The GRWQ seems to partially measure anactual prediction of outcomes by the participant, similar Strengths of this study are the a priori selection of varia- to a general self-efficacy expectation (e.g., how much weight bles to be analyzed as predictors, a unique population do you think you will lose by the end of this program?), while (Portuguese women), and the very low dropout rate. Lim- simultaneously tapping into a more attitudinal facet itations include a moderately-sized sample considering towards a person's weight and weight loss (how happy/ the known measurement error associated with question- accepting/disappointed would you feel at certain levels of weight naire psychological assessments, the fact that some of the loss?). To some extent, the latter could measure idealiza- scales used still lack well-established validity, and the tion of body weight and perceived importance of body absence of a control or comparison group.
weight and shape for self-esteem and well-being. There-fore, it is possible that moderate or "realistic" weight out- come evaluations (i.e. not too accepting but also not Several pretreatment variables were re-evaluated as predic- excessively stringent) are the most beneficial and indeed tors of short-term weight loss in women. Previous dieting, reflect a good balance between a sufficient and necessary low self-motivation, and body size dissatisfaction were sense of self-efficacy and low to moderate levels of thin- confirmed as negative predictors of weight outcomes, ideal internalization, a variable which has been shown to while the relationship of outcome evaluations with be a positive risk factor for body dissatisfaction, negative weight reduction suggested a negative and curvilinear pat- affect, and eating diso tern, with positive but not excessively demanding evalua-tions presaging the best results. These data regarding Women reporting a larger discrepancy between self and people's outcome evaluations prior to weight loss may ideal body figures, which indicates a higher body size dis- have important clinical implications t satisfaction, were less likely to lose weight. In a evidence for such a pattern of association; thus, they await previous report, the same self-ideal measure correlated replication in other samples. Additionally, treatment deci- similarly with short-term results, while two other meas- sions based on level of previous dieting (alone or ures of body image showed comparable, albeit non-signif- included in comprehensive prediction models) may be icant tratment scores in the body possible in the near future, at least for overweight and dissatisfaction scale of the Eating Disorders Inventory, a moderately obese women. The more consistent predictors measure of psychological concern and dislike about one's from this and previous studies (e.g.,) can and body sh negatively associ- should be used in future hypothesis-testing studies of ated with weight loss in two other behavioral weight loss moderators of weight loss. Finally, this study highlights prese relationships may be explained the fact that behavioral and psychological prediction by the negative association of body image with mood and models may, to some extent, be specific to a particular cul- psychological impairme, and also by the disap- . Hence, it is likely that some variables will pointment and lack of self-worth and self-confidence fol- emerge as moderators (and mediators) of obesity treat- lowing previous failed attempts to change weight and ment in some, but not all cultures, while others will be b Although self-esteem did not predict proven as more universal correlates of success.
outcomes, we observed significant correlations betweenbody size dissatisfaction and self-esteem (ρ = -0.18, p = (page number not for citation purposes) International Journal of Behavioral Nutrition and Physical Activity 2004, 1:12
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