Does Weight Loss Maintenance Become Easier Over Time?

Transcription

1 Does Weight Loss Maintenance Become Easier Over Time? Mary L. Klem,* Rena R. Wing,* Wei Lang,* Maureen T. McGuire, and James O. Hill Abstract KLEM, MARY L., RENA R. WING, WEI LANG, MAUREEN T. MCGUIRE, AND JAMES O. HILL. Does weight loss maintenance become easier over time? Obes Res. 2000;8: Objective: Studies of health-related behaviors, including weight loss, have shown that risk of relapse decreases over time, although reasons for this relationship are unclear. The purpose of this cross-sectional study was to determine if subjects who have maintained weight losses for varying periods of time report different strategies for weight loss maintenance or differences in the effort and pleasure associated with weight maintenance behaviors. Research Methods and Procedures: Subjects were 758 women and 173 men who had maintained losses of at least 30 lb (mean 60 lb) for 2 years or longer (mean years). Self-administered questionnaires assessed subjects use of weight maintenance strategies in the past year and their perceptions of the effort, attention, and pleasure associated with weight maintenance. Results: Subjects who had maintained weight losses longer used fewer weight maintenance strategies and reported that less effort was required to diet and maintain weight and that less attention was required to maintain weight. The pleasure derived from exercise, low-fat eating, and maintaining weight was unrelated to duration of weight loss maintenance. Discussion: As duration increases, a shift in the balance between the effort and pleasure of weight maintenance may occur. This shift may increase the likelihood of continued maintenance. Key words: weight loss maintenance, weight maintenance strategies, relapse, costs Submitted for publication December 13, Accepted for publication in final form March 8, The *University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; the University of Minnesota School of Public Health, Minneapolis, Minnesota; and the University of Colorado Health Sciences Center, Denver, Colorado. Address correspondence to Mary Lou Klem, Ph.D., Department of Psychiatry, University of Pittsburgh School of Medicine, 3811 O Hara St., Pittsburgh, PA klemml@msx.upmc.edu Copyright 2000 NAASO Introduction Relatively little is known about factors that may influence the process of successful weight maintenance. Treatment characteristics such as continued therapist contact have been shown to increase the likelihood of weight maintenance (1), and successful weight maintenance has also been correlated with continued consumption of low-fat diets, regular physical activity, and selfmonitoring (2 4). Recently, McGuire and colleagues (5), following participants in a longitudinal study of successful loss weight maintainers (National Weight Control Registry), found that duration of weight maintenance positively predicted the likelihood of continued maintenance of weight. Studies of relapse rates for heroin addiction, smoking, and alcoholism have also shown that risk of relapse decreases over time (6 10). Brownell et al. (11) have speculated that, over time, individuals become protected against relapse through the acquisition of certain critical behaviors or skills. If this is so, individuals in the early stages of weight maintenance might use a wide variety of weight control strategies, whereas individuals further along in the maintenance process might use a smaller set of core habits or adopt a different set of skills that are essential to weight maintenance. Thus, individuals with varying durations of weight maintenance may report differences in the number or type of strategies used to maintain weight. In exploring the relationship between duration of maintenance and continued weight maintenance, it may also be useful to examine the amount of effort or attention required to engage in weight control strategies. Regular exercise and consumption of a low-fat diet, behaviors that are related to weight maintenance, can be conceptualized as habits (tendencies to repeat specific behavioral responses). Behaviors are likely to become habits if they are repeatedly practiced over time within highly similar settings (12). As a behavior is repeatedly practiced, the cognitive processes that initiate and control the behavior (e.g., intentions) become more automatic. As a result, the behavior itself becomes automatic, requiring little conscious effort or attention (12). Although not commonly addressed in theories of habit 438 OBESITY RESEARCH Vol. 8 No. 6 Sept. 2000

2 formation, it also seems possible that the pleasure derived from such behaviors may increase as they become more habitual and hence easier to engage in. Thus, the purpose of this cross-sectional study was to examine, among individuals successful at long-term maintenance of weight loss, the relationship between duration of weight maintenance, strategies used to maintain weight, and the effort, attention, and pleasure associated with weight maintenance behaviors. Research Methods and Procedures Subjects All participants in the National Weight Control Registry (NWCR) who had completed 1-year follow-up assessments (758 women, 173 men) were included in these analyses. Details of the registry have been published elsewhere (13), so only a brief overview of the study methodology is provided here. The NWCR is an observational study of individuals successful at long-term maintenance of weight loss. Individuals are eligible for participation in the registry if they have lost at least 30 lb and have maintained a loss of at least 30 lb for 1 year or longer. Participants are recruited for the registry through public service announcements and coverage of the registry by local and national media. Potential subjects who call a toll-free telephone number are sent informed consent forms to sign and return. Those individuals who return signed consent forms are then mailed questionnaire packets to complete and return. As part of the baseline assessment, subjects report their current age, height, weight, lifetime maximum weight, and the dates at which the weights were reached. Weight information is then used to calculate total weight loss and duration of maintenance of the required 30-lb weight loss. Subjects receive no compensation for their participation. Measures at 1-Year Follow-up The questions of primary interest for this paper (i.e., those assessing the effort and pleasures associated with weight maintenance) were asked at 1-year follow-up (not at entry into the registry). Therefore, all other data used in analyses were also obtained from the 1-year follow-up survey. Demographic and Weight Variables. Subjects reported their current weight (weight at 1-year follow-up) in pounds. Current total weight loss was calculated by subtracting weight at 1-year follow-up from maximum lifetime weight (as reported at baseline), whereas current duration of maintenance of the required 30-lb weight loss was determined by adding 1 year to baseline weight loss duration. Weight change over the past year (since baseline) was calculated by subtracting weight at baseline from weight at 1-year follow-up. Current age was calculated by adding 1 year to a subject s baseline age. A prior study has shown that self-reported weight information from participants in the NWCR has adequate reliability and validity (5). Weight Control Strategies in the Past Year. Using a standard checklist, subjects indicated which of 10 weight control strategies they had used in the past year. Items included keeping healthy foods in the house, decreasing meals out in restaurants, weighing self on regular basis, buying healthrelated books or magazines, and keeping records of food intake or exercise. Responses to the checklist were used to calculate, for each subject, the total number of weight loss strategies used in the past year (0 to 10). Variables were also created, which indicated how many (range 0 to 2) foodrelated strategies (kept few high-fat foods in the house, kept many low-fat foods in the house), and how many (range 0 to 2) friend-related strategies (spent less time with overweight friends, spent more time with normal-weight friends) a subject had used in the past year. Frequency of self-weighing was assessed by having subjects choose a response that best described how often they weighed themselves (several times a day, once per day, several times per week, once per week, less than once per week, less than once per month). Self-reported dietary intake was assessed using the Block Food Frequency Questionnaire (14), a measure that has been shown to correlate with 4-day food records (15). The instrument provides estimates of current total daily energy intake and percentage of daily energy obtained from fat, carbohydrate, and protein. The Paffenbarger Activity Questionnaire (16) was used to assess current activity levels of subjects. This questionnaire, which correlates with levels of cardiovascular fitness (17), provides estimates of total energy expenditure over the past week, as well as estimates of the amount of energy expended through stair-climbing, walking, and light, moderate, and heavy intensity activities. The Effort and Pleasures Associated with Weight Maintenance. Likert-type scales (1 very little/not at all; 8 a lot/extremely) were used by subjects to indicate: 1) how much effort they devote to diet regimen, to exercise regimens, and to weight maintenance; 2) how much attention is required to follow a diet and/or exercise regimen, and to maintain weight; and 3) how much pleasure they derive from exercise, eating low-fat meals, and weight maintenance. In addition, subjects also used Likert-like scales to rate the amount of pleasure derived from several nonweight-related activities. Pleasure ratings for the activities of reading a book, sitting in the sun, listening to music, and watching TV were averaged together to yield an overall rating of the pleasure derived from sedentary activities; similarly, ratings of the pleasure derived from the activities of eating a high-fat meal and going to restaurants were summed and averaged to yield an overall rating of the pleasure derived from higher-fat eating. Finally, the effort ratings for exercise, dieting, and weight OBESITY RESEARCH Vol. 8 No. 6 Sept

3 maintenance were subtracted from the pleasure ratings for these three respective variables. The resulting scores reflected the pleasure associated with exercise, dieting, and weight maintenance relative to the effort required for these activities, with positive scores indicating greater pleasure relative to the effort required. Statistics All analyses were completed using The SAS System for Windows version 6.12 (SAS Institute Inc., Cary, NC). Utilizing duration of maintenance as a continuous variable, linear and logistic regression analyses were used to explore the impact of duration on use of weight maintenance behaviors and the effort and pleasures associated with weight maintenance. Preliminary analyses indicated that duration of maintenance was non-normally distributed, therefore, Spearman rank-order correlation coefficients were used to analyze relationships between duration and other weight and demographic characteristics (total weight loss, current weight, weight change over the past year, current age). For ease of interpretation, results of analyses are presented in tables by tertiles of duration (,, 6 or more years). Due to the exploratory nature of this study, p values were not adjusted for multiple comparisons. Results Preliminary Analyses The total sample of subjects reported currently maintaining an average weight loss of lb and had maintained a 30-lb weight loss for an average of years (range of 2 to 67 years). Spearman rank-order correlations indicated significant relationships between duration of weight maintenance and current age (r s 0.12, p ), current weight (r s 0.24, p ), total weight loss (r s 0.21, p ), and weight change in the past year (r s 0.22, p ). Specifically, subjects with longer duration of weight maintenance were older, weighed less, and had greater total weight loss and smaller weight regain in the past year (Table 1). As a consequence, these variables were controlled for in all subsequent analyses. Weight Control Strategies in the Past Year Linear regression analysis indicated that there was a significant relationship between duration of maintenance and the total number of weight loss strategies used in the past year, with increasing duration associated with use of fewer strategies (p ; Table 2). Subjects with longer duration reported using fewer food-related strategies (p 0.04), but there was no relationship between duration of maintenance and the number of friend-related strategies used. Logistic regression was used to examine the relationship between duration of weight maintenance and use of each of 10 weight control strategies in the past year (Table 2). Subjects with longer duration were less likely to report that they had kept a picture of themselves in a prominent place (p ) or kept records of food intake or exercise (p ). Duration was not related to frequency of self-weighing. For all subjects, the total number of strategies used was significantly correlated with the amount of effort required to follow a diet (r s 0.08, p 0.008) and to maintain weight (r s 0.14, p ), as well as with the amount of attention required for weight maintenance (r s 0.08, p 0.02). Duration of maintenance did not predict average total daily energy intake or percentages of daily energy derived from fats, carbohydrates, and protein. As can be seen in Table 3, all subjects, regardless of duration of weight loss maintenance, reported mean daily intakes of approximately 1400 kcal and obtained 25% to 26% of daily energy from fat. Linear regression analysis indicated that duration was not significantly associated with the total amount of energy expended through physical activity. Participants who had maintained weight losses for longer periods Table 1. Characteristics of NWCR members at 1-year follow-up by tertiles of duration of weight maintenance 6 years (n 319) Current age (years) * Current weight (lbs) * Total weight loss (lbs) * Weight change in past year (lbs) * * Spearman rank-order correlations were significant; all p values were OBESITY RESEARCH Vol. 8 No. 6 Sept. 2000

4 Table 2. Use of weight control strategies in the past year by tertiles of duration of weight maintenance 6 years (n 319) p value Number of strategies used in the past year (mean SD) * Number of food-related strategies (mean SD) Number of friend-related strategies (mean SD) NS Kept few high-fat foods in house (%) NS Kept many healthy foods in house (%) NS Decreased meals eaten in restaurants (%) NS Avoided overweight friends (%) NS Spent more time with normal-weight friends (%) NS Spent more time with friends who exercise (%) NS Kept picture of self in prominent place (%) Weighed on a regular basis (%) NS Kept records of food intake or exercise (%) Bought books/magazines related to nutrition or exercise (%) NS * Linear regression analysis controlled for current age, current weight, total weight loss, and weight change over the past year; unadjusted means are shown; r Logistic regression analyses controlled for current age, current weight, total weight loss, and weight change over the past year; unadjusted means are shown. NS, not statistically significant. reported expending greater percentages of total energy through medium intensity (p ) and light intensity activities (p ). The Effort and Pleasures of Weight Maintenance After adjusting for current age, current weight, total weight loss, and weight change over the past year, duration of weight maintenance was not associated with the degree of effort required to exercise, nor with the amount of attention required to follow a diet/exercise regimen (Table 4). However, subjects with longer durations reported that significantly less effort was required to diet and to maintain weight and that less attention was required to maintain weight (p values of 0.05). Although the effort associated with weight maintenance appears to decrease as duration of weight maintenance increases, the pleasures of weight maintenance appear unaffected by duration. A series of linear regression analyses indicated that duration was not significantly related to the amount of pleasure derived from a regular exercise regimen, eating a low-fat meal, or maintaining weight. Length of maintenance was also not associated with the pleasures of unhealthy behaviors: duration did not predict the pleasure derived from sedentary activities or higher-fat eating. Finally, the effort ratings for exercise, diet, and maintaining weight were subtracted from the pleasure ratings for exercise, low-fat eating, and maintaining weight, respectively. The resulting scores reflected the pleasures of these three activities relative to the effort required to engage in them, with positive scores indicating greater pleasure relative to the effort required. Duration was found to be associated with greater pleasure of weight maintenance, relative to the effort required to maintain weight (p 0.03). There was no effect of duration on the pleasure of exercise relative to the effort required, nor was there an effect of duration on the pleasure of low-fat eating, relative to the effort required to diet. Discussion Little is known about the natural history of attempts to change health-related behaviors. Studies of heroin addiction, smoking, and alcoholism have shown that risk of relapse decreases over time (6 10). However, the mechanisms for this relationship are unclear (11). In the present study, individuals with varying durations of weight maintenance reported differences in the effort and attention required for dieting and maintaining weight. That is, subjects who had maintained weight losses for longer periods of time reported that less effort was required to diet and to maintain weight and that less attention was also required for weight maintenance. This decrease in the burden of maintaining a OBESITY RESEARCH Vol. 8 No. 6 Sept

5 Table 3. Dietary intake and physical activity by tertiles of duration of weight maintenance 6 years (n 319) p value Average daily intake (kcal) NS* % of kcal from: Fat NS Carbohydrate NS Protein NS Average weekly expenditure (kcal) NS kcal expended through: Flights of stairs climbed NS Blocks walked NS Light intensity Medium intensity Heavy intensity NS * NS, not statistically significant. Linear regression analysis controlled for current age, current weight, total weight loss, and weight change over the past year, unadjusted means are shown; r 2 for light intensity and r 2 for medium intensity weight loss, coupled with no change in the associated pleasures, may facilitate continued maintenance of weight loss. The decreased effort associated with weight maintenance does not appear to be due to differences in dietary intake or physical activity levels: no effect of duration was observed for calorie intake or overall energy expenditure. However, the limitations of self-reported activity levels and dietary intake are well-known (18). It is possible that more accurate measures of actual energy intake and expenditure (e.g., doubly labeled water) might reveal a relationship between these factors and the effort or attention required for weight maintenance. Apparent decreases in the effort associated with weight maintenance may be due to decreases in the number of weight control strategies used by subjects. Subjects with longer durations of weight maintenance were less likely to report use of record keeping and placing a picture of oneself in a prominent place, and used fewer food-related strategies, than subjects of shorter duration. It may be that, over time, successful weight loss maintainers need to rely less on use of such strategies. In addition, the strategies successful weight losers do use may become habitual and thus require minimal attention or conscious effort (12). Further studies of the strategies used by weight maintainers would help to clarify this issue. It should be noted that, although the effort and attention required to maintain a weight loss were greatest in the early stages of weight maintenance, the amount of effort and attention required consistently appeared to be rated as less than the amount of pleasure derived from successful weight control. It is unclear if the scales used to rate these concepts are truly equivalent (e.g., that a rating of 2 on the effort scale is equal to a rating of 2 on the pleasure scale). Nonetheless, this finding suggests that even subjects with the shortest duration may believe that the satisfaction of weight maintenance outweighs the effort associated with it. To the best of our knowledge, this is the first study to examine the effort and pleasures associated with weight maintenance. Our findings are strengthened by the large sample size and our ability to study the habits of individuals already well into the weight maintenance process. However, a clear limitation is the cross-sectional nature of this study, which prevents us from ruling out alternative explanations of our findings. It is possible that, among individuals who lose weight, those who initially find maintenance to be taxing and unpleasurable may be less likely to continue to maintain their weight losses, and so may not be represented in the registry. There may also have been other differences at the onset of weight maintenance that have influenced subjects perceptions of the effort and pleasures associated with weight maintenance. For example, although subjects in the highest tertile of duration are older than subjects in the lower tertiles, this difference in mean age is not as great as the differences in duration of maintenance (see Table 1). 442 OBESITY RESEARCH Vol. 8 No. 6 Sept. 2000

6 Table 4. The effort and pleasures of weight maintenance by tertile of duration* p values 6 years (n 319) unadj. adj. Effort required for: Exercise Diet Maintaining weight Attention required for: Following diet/exercise regimen Maintaining weight Pleasure derived from: Exercise Low-fat meal Maintaining weight Sedentary activities Higher-fat eating * Scores ranged from 1 to 8, with higher scores indicating greater effort, attention or pleasure. p values are from univariate linear regression analyses and from linear regression analyses controlling for current age, current weight, total weight loss, and weight change over the past year; unadjusted means are shown. r r r Thus, subjects in the highest tertile were younger at the time of initial weight loss and onset of maintenance. Similarly, although these subjects have had more time in which to regain weight, they currently weigh less and are maintaining greater weight losses than subjects with shorter duration. This suggests that they may have achieved greater weight losses initially or regained less weight in the early stages of weight maintenance. A longitudinal study of weight loss maintainers would provide further insight about the role of such differences in subjects perceptions of the effort and pleasure associated with successful weight maintenance. In summary, duration of weight maintenance is inversely related to the costs and unrelated to the pleasures of weight maintenance. As duration of maintenance increases, a shift in the balance between effort and pleasure may occur. This shift may, in turn, increase the likelihood of continued weight maintenance. Acknowledgments This study was supported by the International Life Sciences Institute North America (ILSI N.A.) Project Committee on Diet and Obesity. The opinions expressed herein are those of the authors and do not necessarily represent the views of ILSI N.A. References 1. Perri MG, Nezu AM, Patti et al. Effect of length of treatment on weight loss. J Consult Clin Psych. 1989;57: Jeffery RW, Bjornson-Benson WM, Rosenthal BS, et al. Behavioral treatment of obesity with monetary contracting: Two-year follow-up. Addict Behav. 1984;9: Kayman S, Bruvold W, Stern JS. Maintenance and relapse after weight loss in women: behavioral aspects. Am J Clin Nutr. 1990;52: Pronk NP, Wing RR. Physical activity and long-term maintenance of weight loss. Obes Res. 1994;2: McGuire MT, Wing RR, Klem ML, Hill JO. What predicts weight regain among a group of successful weight losers? J Consult Clin Psych. 1999;67: Hunt WA, Barnett LW, Branch LG. Relapse rates in addiction programs. J Clin Psych. 1971;27: Becona E, Vasquez FL. The course of relapse across 36 months for smokers from a smoking-cessation program. Psychol Rep. 1998;82: OBESITY RESEARCH Vol. 8 No. 6 Sept

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