António Palmeira

Mediators of Weight Loss and Weight Loss Maintenance in Middle-aged Women

Long‐term behavioral self‐regulation is the hallmark of successful weight control. We tested mediators of weight loss and weight loss maintenance in middle‐aged women who participated in a randomized controlled 12‐month weight management intervention. Overweight and obese women (N = 225, BMI = 31.3 ± 4.1 kg/m2) were randomly assigned to a control or a 1‐year group intervention designed to promote autonomous self‐regulation of body weight. Key exercise, eating behavior, and body image variables were assessed before and after the program, and tested as mediators of weight loss (12 months, 86% retention) and weight loss maintenance (24 months, 81% retention). Multiple mediation was employed and an intention‐to‐treat analysis conducted. Treatment effects were observed for all putative mediators (Effect size: 0.32–0.79, P < 0.01 vs. controls). Weight change was −7.3 ± 5.9% (12‐month) and −5.5 ± 5.0% (24‐month) in the intervention group and −1.7 ± 5.0% and −2.2 ± 7.5% in controls. Change in most psychosocial variables was associated with 12‐month weight change, but only flexible cognitive restraint (P < 0.01), disinhibition (P < 0.05), exercise self‐efficacy (P < 0.001), exercise intrinsic motivation (P < 0.01), and body dissatisfaction (P < 0.05) predicted 24‐month weight change. Lower emotional eating, increased flexible cognitive restraint, and fewer exercise barriers mediated 12‐month weight loss (R2 = 0.31, P < 0.001; effect ratio: 0.37), but only flexible restraint and exercise self‐efficacy mediated 24‐month weight loss (R2 = 0.17, P < 0.001; effect ratio: 0.89). This is the first study to evaluate self‐regulation mediators of weight loss and 2‐year weight loss maintenance, in a large sample of overweight women. Results show that lowering emotional eating and adopting a flexible dietary restraint pattern are critical for sustained weight loss. For long‐term success, interventions must also be effective in promoting exercise intrinsic motivation and self‐efficacy.

Motivation, self-determination, and long-term weight control

This article explores the topics of motivation and self-regulation in the context of weight management and related behaviors. We focus on the role of a qualitative approach to address motivation - not only considering the level but also type of motivation - in weight control and related behaviors. We critically discuss the operationalization of motivation in current weight control programs, present a complementary approach to understanding motivation based on self-determination theory, and review empirical findings from weight control studies that have used self-determination theory measures and assessed their association with weight outcomes. Weight loss studies which used Motivational Interviewing (MI) are also reviewed, considering MIs focus on enhancing internal motivation. We hypothesize that current weight control interventions may have been less successful with weight maintenance in part due to their relative disregard of qualitative dimensions of motivation, such as level of perceived autonomy, often resulting in a motivational disconnect between weight loss and weight-related behaviors. We suggest that if individuals fully endorse weight loss-related behavioral goals and feel not just competent but also autonomous about reaching them, as suggested by self-determination theory, their efforts are more likely to result in long-lasting behavior change.

Predicting short-term weight loss using four leading health behavior change theories

BackgroundThis study was conceived to analyze how exercise and weight management psychosocial variables, derived from several health behavior change theories, predict weight change in a short-term intervention. The theories under analysis were the Social Cognitive Theory, the Transtheoretical Model, the Theory of Planned Behavior, and Self-Determination Theory.MethodsSubjects were 142 overweight and obese women (BMI = 30.2 ± 3.7 kg/m2; age = 38.3 ± 5.8y), participating in a 16-week University-based weight control program. Body weight and a comprehensive psychometric battery were assessed at baseline and at programs end.ResultsWeight decreased significantly (-3.6 ± 3.4%, p < .001) but with great individual variability. Both exercise and weight management psychosocial variables improved during the intervention, with exercise-related variables showing the greatest effect sizes. Weight change was significantly predicted by each of the models under analysis, particularly those including self-efficacy. Bivariate and multivariate analyses results showed that change in variables related to weight management had a stronger predictive power than exercise-specific predictors and that change in weight management self-efficacy was the strongest individual correlate (p < .05). Among exercise predictors, with the exception of self-efficacy, importance/effort and intrinsic motivation towards exercise were the stronger predictors of weight reduction (p < .05).ConclusionThe present models were able to predict 20–30% of variance in short-term weight loss and changes in weight management self-efficacy accounted for a large share of the predictive power. As expected from previous studies, exercise variables were only moderately associated with short-term outcomes; they are expected to play a larger explanatory role in longer-term results.

Who will lose weight? A reexamination of predictors of weight loss in women

BackgroundThe 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.MethodsSubjects 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.ResultsOf all starting participants, 3.5% (5 subjects) did not finish the program. By treatments 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.ConclusionsSeveral 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.

Reciprocal effects among changes in weight, body image, and other psychological factors during behavioral obesity treatment: a mediation analysis.

BackgroundChanges in body image and subjective well-being variables (e.g. self-esteem) are often reported as outcomes of obesity treatment. However, they may, in turn, also influence behavioral adherence and success in weight loss. The present study examined associations among obesity treatment-related variables, i.e., change in weight, quality of life, body image, and subjective well-being, exploring their role as both mediators and outcomes, during a behavioral obesity treatment.MethodsParticipants (BMI = 31.1 ± 4.1 kg/m2; age = 38.4 ± 6.7 y) were 144 women who attended a 12-month obesity treatment program and a comparison group (n = 49), who received a general health education program. The intervention included regular group meetings promoting lasting behavior changes in physical activity and dietary intake. Body image, quality of life, subjective well-being, and body weight were measured at baseline and treatments end. Mediation was tested by multiple regression and a resampling approach to measure indirect effects. Treatment group assignment was the independent variable while changes in weight and in psychosocial variables were analyzed alternatively as mediators and as dependent variables.ResultsAt 12 months, the intervention group had greater weight loss (-5.6 ± 6.8% vs. -1.2 ± 4.6%, p < .001) and larger decreases in body size dissatisfaction (effect size of 1.08 vs. .41, p < .001) than the comparison group. Significant improvements were observed in both groups for all other psychosocial variables (effect sizes ranging from .31–.75, p < .05). Mediation analysis showed that changes in body image and body weight were concurrently mediators and outcomes of treatment, suggesting reciprocal influences. Weight loss partially mediated the effect of treatment on quality of life and on self-esteem but the reciprocal effect was not observed.ConclusionChanges in weight and body image may reciprocally affect each other during the course of behavioral obesity treatment. No evidence of reciprocal relationships was found for the other models under analysis; however, weight changes partially explained the effects of treatment on quality of life and self-esteem. Weight and psychosocial changes co-occur during treatment and will probably influence each other dynamically, in ways not yet adequately understood. Results from this study support the inclusion of intervention contents aimed at improving body image in weight management programs.

Usefulness of different techniques for measuring body composition changes during weight loss in overweight and obese women

The objective was to compare measures from dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and anthropometry with a reference four-compartment model to estimate fat mass (FM) and fat-free mass (FFM) changes in overweight and obese women after a weight-loss programme. Forty-eight women (age 39.8 +/- 5.8 years; weight 79.2 +/- 11.8 kg; BMI 30.7 +/- 3.6 kg/m2) were studied in an out-patient weight-loss programme, before and after the 16-month intervention. Women attended weekly meetings for the first 4 months, followed by monthly meetings from 4 to 12 months. Body composition variables were measured by the following techniques: DXA, anthropometry (waist circumference-based model; Antrform), BIA using Tanita (TBF-310) and Omron (BF300) and a reference four-compartment model. Body weight decreased significantly ( - 3.3 (sd 3.1) kg) across the intervention. At baseline and after the intervention, FM, percentage FM and FFM assessed by Antrform, Tanita, BF300 and DXA differed significantly from the reference method (P < or = 0.001), with the exception of FFM assessed by Tanita (baseline P = 0.071 and after P = 0.007). DXA significantly overestimated the change in FM and percentage FM across weight loss ( - 4.5 v. - 3.3 kg; P 0.05) from the reference model in any body composition variables. We conclude that these methods are widely used in clinical settings, but should not be applied interchangeably to detect changes in body composition. Furthermore, the several clinical methods were not accurate enough for tracking body composition changes in overweight and obese premenopausal women after a weight-loss programme.

Change in body image and psychological well-being during behavioral obesity treatment: Associations with weight loss and maintenance

This study reports on outcomes from a behavioral obesity treatment program, evaluating if treatment-related changes in body image and psychological well-being are predictors of weight change during treatment and after follow-up. Participants were 142 overweight/obese women (BMI=30.2+/-3.7kg/m(2); age=38.3+/-5.8 years) participants in a behavioral treatment program consisting of a 4-month treatment period and a 12-month follow-up. Psychosocial variables improved during treatment and these changes were correlated with 4-month weight reduction. Short-term changes in body size dissatisfaction (p=.002) and mood (p=.003) predicted long-term weight loss. Additional results suggest that there might be a predictive role of short-term changes in body size dissatisfaction and self-esteem on long-term weight loss after accounting for initial weight change (p<.028). We conclude that, along with weight changes, cognitive and affect-related processes influenced during obesity treatment may be related long-term success, in some cases independently of initial weight loss.

The role of self-determination theory and motivational interviewing in behavioral nutrition, physical activity, and health: an introduction to the IJBNPA special series.

On the occasion of the 9 Annual Meeting of the International Society of Behavioral Nutrition and Physical Activity (ISBNPA) in Lisbon (2009), a satellite meeting was organized in Sintra entitled Self-Determination Theory and Motivational Interviewing in Behavioral Nutrition, Physical Activity, and Health. The organizers of this small meeting (about 100 people attended) were interested in stimulating a focused discussion around the similarities, differences, and complementary of selfdetermination theory (SDT; [1]) and Motivational Interviewing (MI; [2]). This gathering was spurred by both a recent growth in applied health behavior research based in SDT [3], and by a continuing interest in exploring the mechanisms by which MI produces results in practice [4]. The links between SDT, a well-established theory of human motivation and behavior, and MI, a popular clinical method for evoking behavior change are multiple and have been explored before [5,6], leading many to think that a formal “marriage” i.e., accepting SDT as “the theory of MI” and MI as the “intervention method of SDT” would be just a matter of time. Both models are explicitly person-centered and process-oriented, both emphasize that optimal behavior change must involve deep personal commitment and engagement, and both stress that a positive emotional “climate”, defined by genuine empathy and unconditional regard towards patients or clients is a necessary condition for the success of behavior change interventions, especially their long-term effects. Moreover, both SDT and MI appear to have at its center the concept of motivation, endorsing the development of “internal” motives and the need for patients to take responsibility for change, to the detriment of externally imposed goals, pressures, or a preponderance of reasons for change which are nor personally meaningful [7,8]. The interest in both MI and SDT has grown steadily over the past decades, with scholars and practitioners working in fields such as eating behavior (e.g., [9]), physical activity (e.g., [10]), and diabetes (e.g. [11]), becoming increasingly interested in exploring motivational dynamics. It is recognized that the motivation underlying patients’ behavior change attempts provides them the necessary energy to actually undertake change and plays a key role in successful long-term outcomes. In fact, the issue of behavioral persistence is a critical one in the era of behavioral, preventive, and “lifestyle” medicine, with individuals increasingly called upon to manage or “self-regulate” their own health [12]. Short-lived change, such as what results from so many weight loss programs, is not what health practitioners and their patients are usually looking for. According to SDT, although patients and clients might put some initial effort in change, lasting results are more likely to fail if it is not undergirded by the ‘right’ motives [13]. This implies that it is critical to move beyond merely considering a patient’s level or intensity of motivation but also consider the quality of their motivation. In fact, motivation is conceived by SDT as a differentiated concept and a distinction is made between different types of motivation (autonomous relative to controlled), with some motivational subtypes being more desirable because they yield more positive outcomes than other types. Specifically, SDT researchers maintain that patients can best self-endorse change such that they willingly or volitionally pursue it rather than feeling seduced or pressured to make those changes. Nevertheless, and despite recent progress (e.g., [14]), * Correspondence: pteixeira@fmh.utl.pt Interdisciplinary Centre for the Study of Human Performance, Faculty of Human Kinetics, Technical University of Lisbon, Lisbon, Portugal Full list of author information is available at the end of the article Teixeira et al. International Journal of Behavioral Nutrition and Physical Activity 2012, 9:17 http://www.ijbnpa.org/content/9/1/17

Factorial Validity and Invariance Testing of the Exercise Dependence Scale-Revised in Swedish and Portuguese Exercisers

The present study investigated the factorial validity and factorial invariance of the 21-item Exercise Dependence Scale-Revised using 162 Swedish and 269 Portuguese exercisers. In addition, the prevalence of exercise dependence symptoms and links to exercise behavior, gender, and age in the two samples was also studied. Confirmatory factor analyses demonstrated that the hypothesized 7-factor model made a good fit to data in both samples. Multi-sample analyses supported partial measurement invariance across the samples; only factor loadings involving items 3 and 19 were noninvariant. The “Reduction in Other Activities” and “Lack of Control” factors were the most problematic scales in terms of average variance explained and reliability measures of weighted omega and Cronbachs alpha. In total, 9.2% of the Swedish sample and 5.2% of the Portuguese sample were classified as at risk for exercise dependence. Overall, the results support the factorial validity of the translated Exercise Dependence Scale-Revised in samples outside North-America, although more research is needed.

Cross-sectional and prospective associations between moderate to vigorous physical activity and sedentary time with adiposity in children.

Background:Physical activity (PA) and sedentary time (SED) have both been suggested as potential risk factors for adiposity in children. However, there is paucity of data examining the temporal associations between these variables.Objective:This study aimed to analyze the cross-sectional and prospective associations between PA, SED and body composition in children.Methods:A total of 510 children (age at baseline 10.1±0.8, age at follow-up 11.8±0.9) from six Portuguese schools from the Oeiras Municipality participated in this study. PA and SED were measured by accelerometry and trunk fat mass (TFM) and body fat mass (BFM) were measured by dual energy X-ray absorptiometry. Fat mass index (FMI) was calculated as BFM divided by height squared. Several regression models adjusted for age, sex, maturity status, follow-up duration, baseline levels of the outcome variable and SED or moderate to vigorous PA (MVPA) were performed.Results:MVPA (min per day) was cross-sectionally inversely associated with adiposity indexes (FMI, TFM and BFM). Adiposity indexes were inversely associated with time in MVPA. In prospective analyses, MVPA was associated with a lower levels of FMI (β=−0.37, 95% confidence interval (CI): −0.49 to −0.26, P<0.001), TFM (β=−0.20, 95% CI: −0.29 to −0.10, P<0.001) and BFM (β=−0.37, 95% CI: −0.49 to −0.26, P<0.001). When the model was adjusted for age, sex, maturity status and for baseline levels of the outcome variables MVPA remained a significant predictor of lower adiposity indexes (FMI: β=−0.09, 95% CI: −0.16 to −0.01, P<0.05; TFM: β=−0.08, 95% CI: −0.15 to −0.01, P<0.05; BFM: β=−0.07, 95% CI: −0.15 to 0.00, P<0.05). Adiposity was not associated with MVPA when modeled as the exposure in prospective analyses. SED was not related with adiposity indexes, except for the relationship with FMI.Conclusions:In cross-sectional and prospective analyses, MVPA is associated with lower adiposity independent of covariates and SED. Results suggest that promoting MVPA is important for preventing gain in adiposity in healthy children.