The Impact of Regular Self-weighing on Weight Management: A Systematic Literature Review

Background Regular self-weighing has been a focus of attention recently in the obesity literature. It has received conflicting endorsement in that some researchers and practitioners recommend it as a key behavioral strategy for weight management, while others caution against its use due to its potential to cause negative psychological consequences associated with weight management failure. The evidence on frequent self-weighing, however, has not yet been synthesized. The purpose of this paper is to evaluate the evidence regarding the use of regular self-weighing for both weight loss and weight maintenance. Methods A systematic literature review was conducted using the MEDLINE, CINAHL, and PsycINFO online databases. Reviewed studies were broken down by sample characteristics, predictors/conditions, dependent measures, findings, and evidence grade. Results Twelve studies met the inclusion/exclusion criteria, but nearly half received low evidence grades in terms of methodological quality. Findings from 11 of the 12 reviewed studies indicated that more frequent self-weighing was associated with greater weight loss or weight gain prevention. Specifically, individuals who reported self-weighing weekly or daily, typically over a period of several months, held a 1 to 3 kg/m2 (current) advantage over individuals who did not self-weigh frequently. The effects of self-weighing in experimental studies, especially those where self-weighing behaviors could be isolated, were less clear. Conclusion Based on the consistency of the evidence reviewed, frequent self-weighing, at the very least, seems to be a good predictor of moderate weight loss, less weight regain, or the avoidance of initial weight gain in adults. More targeted research is needed in this area to determine the causal role of frequent self-weighing in weight loss/weight gain prevention programs. Other open questions to be pursued include the optimal dose of self-weighing, as well as the risks posed for negative psychological consequences.


Background
Excess body weight is a leading cause of death in the U.S. [1,2], contributing to the development or complication of many chronic diseases including heart disease, diabetes, and cancer [3,4] Fortunately, even a modest amount of weight loss has been shown to reduce the incidence of chronic diseases and improve obesity-related health conditions [5]. Many people who have experienced weight issues have learned to manage their weight over the longterm via sustained, moderate caloric restriction and regular physical activity [6]. Poor adherence to these behaviors, however, is the norm for individuals attempting to lose weight or maintain weight loss [7] due to substantial physiological [8], environmental [9][10][11], and motivational barriers [12].
Because of the inherent challenges associated with losing weight or preventing weight regain, many people turn to some form of external assistance (e.g., clinical counseling program, community support group, self-help book) to help them initiate or maintain the behavior changes required to lose weight. A major component of these forms of assistance involves instruction in behavioral selfmanagement skills like goal-setting or stimulus control. In particular, regular self-monitoring of weight has been recommended as a key component of behavioral self-regulation of body weight [5].
Regular self-weighing seems to be a common strategy for individuals who have been successful at losing weight and keeping it off. Klem and colleagues [13] found that 75 percent of a cohort of weight loss maintainers report selfweighing at least weekly. Weekly self-weighing also seems to be more common among individuals who lost weight on their own versus using an organized weight management program [14]. In contrast, the prevalence of selfweighing in the general population of healthy weight individuals is not well studied, but one study estimated that about 39 percent self-weigh weekly [15].
Frequent self-weighing is conceptualized to work via behavioral self-regulation [16]. Specifically, an individual who self-weighs often is believed to stay focused on and sensitive to changes in their weight. This creates more opportunities for self-reinforcement of even small weight loss (or weight maintenance) progress. Also, the individual is empowered to quickly identify lapses in their progress and adjust their behavior accordingly to head off substantial weight gain [17].
Despite a plausible rationale, there remains considerable debate on the utility of self-weighing in the context of weight management. Some researchers and practitioners urge caution in the use of frequent self-weighing, at least with some individuals, because it is believed to produce negative psychological conditions such as depression, anxiety, or otherwise unhealthy preoccupations and stress associated with weight [18,19]. Furthermore, the downstream effect of these psychological conditions produced by frequent self-weighing is believed to undermine the effectiveness of weight management interventions by negatively influencing body image and increasing program attrition. Others, however, have noted that most investigations that have observed negative psychological harms secondary to frequent self-weighing have done so only in non-overweight samples [20] and several studies have shown a strong positive association between self-weighing frequency and magnitude of weight loss.
The findings on the utility of regular self-weighing for weight management have yet to be critically reviewed or synthesized. Therefore, the purpose of this paper was to conduct a systematic review of the literature from observational and experimental studies on self-weighing in order to gauge the effectiveness of regular self-weighing on weight loss and weight maintenance (including primary weight gain prevention) in adults. The central research questions examined are: (1) Do the benefits of frequent self-weighing, in terms of body weight, outweigh the disadvantages, and (2) Do the conclusions in this regard differ by the subgroups of individuals who are interested in weight loss or weight maintenance? We hypothesize that the preponderance of evidence would support the use of frequent self-weighing behaviors to promote both weight loss and prevention of weight (re)gain. Implications in the context of weight loss research and clinical practice are also discussed.

Methods
A systematic review of the literature was conducted. MEDLINE, CINAHL, and PsycINFO online databases were searched via the University of Minnesota's Ovid interface http://www.biomed.lib.umn.edu/ovidweb/ ovidweb.cgi to produce relevant articles on self-weighing and weight management. The reference sections of all included studies were also manually searched.

Inclusion and Exclusion Criteria
Inclusion criteria were: English language, adult participants, assessment of body weight, assessment of selfweighing frequency (i.e., used as a treatment component, predictor, or outcome variable), quantitative analysis of the relationship between self-weighing and body weight, and published before January 1, 2008. Since the research question was relatively broad and the body of evidence was expected to be small, no restrictions were placed on sample size, setting, research design, body weight of participants, or length of measurement follow-up. The MEDLINE search included one Medical Subject Heading, Body Weight, along with two text words; self-weighing or self-monitoring. Limiters included English language, humans, and adult population. Keywords used in the Psy-cINFO search included obesity, body weight, weight loss, self-weighing, and self-monitoring (limiters included English language, humans, and adult population).

Data Extraction
The outcome of interest was body weight or change in body weight. For each study, the most conservative approach to data extraction was taken by reporting only findings from the final follow-up visit, and, where possible, only those that were statistically adjusted for potential disturbance variables. To maintain the focus on the scope of the research question of interest, psychological outcomes believed to be related to self-weighing (e.g., depression, obsessive-compulsive disorder, binge eating, body image disorder) were not described. Several investigations on such negative psychological consequences secondary to self-weighing have appeared recently in the scientific literature, therefore the authors agreed this question would be best served by a separate review paper focused on that topic.

Data Synthesis
Studies were broken down by sample characteristics, predictors/conditions, dependent measures, findings, and evidence grade. A previously used adaptation of the American Diabetes Association's (ADA) evidence grading system was used (see Table 1) [21,22]. Studies were assigned an evidence grade of A, B, or C along with a strength grade of 1, 2, or 3 depending on methodological quality, sup- 3 Uncertain benefit to persons at-risk a. evidence from randomized clinical trials with one or more major or three or more minor methodological flaws that could confound results b. evidence from observational studies with high potential for bias c. evidence from case series or case reports 6. Conflicting results with the weight of the evidence supporting the recommendation 7. Expert consensus or clinical experience without support from research studies porting evidence, and estimated benefits to the population at-risk.

Study Characteristics
As outlined in Figure 1, 249 articles were returned from the initial searches of the online databases. Twelve studies [23][24][25][26][27][28][29][30][31][32][33][34] were included in the review per the inclusion/ exclusion criteria and the reasons for exclusion are also given in Figure 1. With the exception of one study that exclusively recruited males [31], all other study samples primarily included middle-aged females. Four studies recruited females exclusively [24,25,27,33] and two studies were conducted in Japan [33,34]. Median baseline body mass index (BMI) was about 30 kg/m 2 across all samples (see Table 2).
The reviewed studies were almost evenly split in their focus on either weight loss or weight maintenance. Body weight was self-reported in all three cross-sectional studies and one of the prospective cohort studies, while all other studies used objective assessments of body weight. Selfweighing, when assessed independently as a predictor variable (versus implicitly as part of a treatment package), was done so exclusively by self-report.

Research Quality
Using the ADA-adapted evidence grading system [21,22], only one study provided A-level evidence in terms of methodological quality [30]. All other studies provided Bor C-level evidence, primarily due to weaker research designs, high non-response or loss to follow-up, underpowered samples, and/or incomplete statistical analyses. With strength grades of 1, the studies by Linde et al. [26] and Levitsky et al. [28] provided the strongest (positive) associations between self-weighing and weight management. Six studies received strength grades of 2, while the remaining four studies received strength grades of 3.

Self-weighing and Weight Maintenance
All three cross-sectional studies indicated a significant association between the frequency of self-weighing and body weight. Specifically, nationally representative samples revealed that, relative to respondents who did not maintain their weight loss, about 60 [25] and 80 [29] percent more respondents who were successful at keeping their weight off reported weekly or daily self-weighing, respectively. The study by Linde et al. [27] indicated that women who reported daily self-weighing weighed nearly 2 BMI units less than women who reported never selfweighing.
Similar to the results observed in her cross-sectional analysis [27], Linde et al. [26] also found that participants in the Pound of Prevention [15] cohort analysis who reported daily self-weighing at the two-year follow-up weighed nearly 2 BMI units less than participants who reported never self-weighing. Butryn et al. [23] found that participants who increased their frequency of self-weighing (unspecified magnitude of increase) over one year gained 2.5 kg less weight relative to participants who decreased their frequency of self-weighing over this same time period.
Two randomized-controlled trials focused on weight maintenance. Secondary analyses by Wing and colleagues [30] found that, in both study treatment conditions, 41 to 55 percent fewer participants who self-weighed daily regained ≥ 2.3 kg relative to participants who did not selfweigh daily. In two separate, short-term experiments conducted by Levitsky et al. [28] a 3 kg weight advantage was noted for college females who received a daily self-weighing and feedback intervention relative to participants who received information-only or assessment-only treatments.

Self-weighing and Weight Loss
In terms of weight loss, a prospective cohort analyses by Linde et al. [26] found that participants in the Weigh To Be trial [35] who self-weighed daily lost about 1 BMI unit more than participants who self-weighed weekly and nearly 3 BMI units more than participants who did not self-weigh at all. Jeffery and colleagues [31] found that, after two years, participants in a 15-week behavioral weight loss program who reported daily self-weighing lost about 15 pounds more than participants who reported self-weighing less than daily. Qi et al. [24] found that, compared to participants who did not lost 5 kg or more, participants who lost 5 kg or more in a behavioral weight loss program significantly increased their daily self-weighing frequency between baseline and 6-months follow-up. An uncontrolled cohort study by Tanaka and colleagues [33] found that participants who completed a nutritionfocused weight loss program whereby they self-weighed 4 times per day lost a significant amount of weight (~4 kg) over 16 weeks.
Two randomized-controlled trials isolated the effects of frequent self-weighing on weight loss by comparing it to an identical intervention that contained everything but the self-weighing component. These two trials found conflicting results. Heckerman and colleagues [32] found no advantage of frequent self-weighing above and beyond a standard 10-week behavioral weight loss program. Fujimoto and colleagues [34], however, found that a group that self-weighed very frequently (4 times daily) lost twice as much weight over a two year period relative to a group that received behavioral weight loss therapy alone. Participants completed a 6-month behavioral weight loss intervention. After the weight loss program, participants were then stratified by the predictors: 1) Weight loss (> 5 kg, ≤ 5 kg) Outcomes were assessed at baseline and 6-months follow-up. They were reported as pre-post-scores (versus change scores) 1) Daily self-weighing score (1-less frequent to 5-more frequent) 50 (100%) participants were available for the 6month follow-up. Participants who lost > 5 kg during treatment observed a significant pre-post increase in their daily self-weighing score (1.7 to 2.5).
C3 -Participants who lost > 5 kg had significantly increased their frequency of selfweighing, but post scores were statistically indistinguishable between groups. Interpretation of the findings was complicated because only the average scaled scores for self-weighing were reported (versus response distributions). Also, no multivariate adjustments were made in the analysis despite the small sample and several significant baseline differences between groups.
McGuire, et al. (2007)  The Pound of Prevention trial involved a general population with an intervention focused on weight gain prevention. The Weigh to Be trial involved an overweight population with a telephone-based intervention focused on weight loss. Predictors included: 1) Self-weighing frequency (Never, Semi-monthly, Monthly, Weekly, Daily) Outcomes were assessed at baseline, 12-, and 24months follow-up for both samples.
In the Pound of Prevention sample, 992 (81%) participants were available for the 24-month follow-up. Participants who self-weighed daily (-0.8) lost significantly more body mass relative to participants who self-weighed weekly (0.3), monthly (0.8), semi-monthly (0.8), or never (1.1). Also, participants who self-weighed weekly gained significantly less body mass relative to participants who self-weighed monthly, semi-monthly, or never.
In the Weigh to Be sample, 1,000 (56%) participants were available for the 24-month follow-up. Participants who self-weighed daily (-1.9) lost significantly more body mass relative to participants who self-weighed weekly (-1.0), monthly (-0.2), semi-monthly (0.2), or never (0.8). Also, participants who self-weighed weekly lost significantly more body mass relative to participants who self-weighed monthly, semimonthly, or never. Participants who never selfweighed gained significantly more weight relative to participants who self-weighed semimonthly or monthly. Note that findings were estimated from study graphs because precise means were not reported.
B1 -After adjustment for several potential confounders, there was clear benefit for both weight maintenance and weight loss with more frequent self-weighing reported at the 24-month follow-ups. The long follow-up and large sample sizes were strengths in both samples, but attrition bias was especially concerning in the Weight to Be sample. Outcomes were assessed at survey completion.

1) Daily self-weighing (%)
The overall survey response rate was 70% and 1,958 participants had complete data for the analysis and fit into the predictor categories. A significantly greater proportion of Successful weight losers (20) reported self-weighing daily relative to non-successful weight losers (11).
C3 -After adjustment for potential confounders, there were significantly more successful weight losers that reported daily selfweighing. There were several potential biases, however, in regard to the vague measurement and definition of a successful weight loser, as well as the exclusion of many respondents who were not believed to fit this definition. Participants completed a 15-week, groupcounseling based behavioral weight loss intervention. Predictors included: 1) Self-weighing frequency (Daily, Less than daily) Outcomes were assessed at baseline, posttreatment, 1-year, and 2-years. 1) ΔBody weight (lb) 81 (91%) participants were available for the 2year follow-up. Participants who self-weighed daily (-17.1) lost significantly more weight at the 2-year follow-up relative to participants who self-weighed less than daily (-6.7).
B2 -There was significant weight loss benefits to participants who self-weighed daily at 2-years follow-up. Strengths included the long follow-up period. The analysis of self-weighing was done in a univariate fashion, however, and it was not clear if self-weighing was beneficial beyond the 1-year follow-up in the multivariate analyses that accounted for confounders.  32 23 overweight participants recruited in Rhode Island. The mean age was 47 years and 87% of the sample was female. Mean baseline BMI was not reported, but participants averaged 72% overweight. Randomized-controlled trial Weight loss Study conditions included: 1) Weigh-in -• Weekly weigh-ins for 10 weeks, followed by monthly weigh-ins for 6 months • Weekly group-based treatment sessions for 10 weeks followed by monthly treatment sessions for 6 months • Treatment sessions included instruction in stimulus control, self-monitoring, and eating/ exercise advice • Instruction to self-weigh frequently between treatment sessions 2) No Weigh-in -• Same as the Weigh-in group, but weigh-ins only conducted at baseline, as well as the end of the treatment and follow-up phases • Instructed not to self-weigh between sessions Outcomes were assessed at baseline, 10-, and 34weeks follow-up. 1) ΔBody weight (lb) 7 (30%) participants completed the 34-week follow-up. No significant differences were observed.
B3 -Participants in the No Weigh-in group actually lost more weight and were more likely to attend the follow-up visits, but the study was severely limited by a small sample size and attrition bias. B2 -The intervention was beneficial over 2 years in that the group that included weight charting 4 times daily lost significantly more weight relative to the group that received behavior therapy alone. Strengths included the long follow-up period. Generalizability may be questionable, however, given the intensity of the self-weighing protocol and the lack of process data documenting the observed (versus assigned) frequency of self-weighing. Also, methodological weaknesses included the vague description of some treatment procedures and stratification of the sample that severely reduced power.

Discussion
In all but one of the twelve reviewed studies, frequent selfweighing (defined as self-weighing weekly or daily), or treatment groups that utilized frequent self-weighing, was associated with significantly greater weight loss, weight maintenance, or less body weight in general relative to infrequent self-weighing. Generally speaking, weekly and daily self-weighers held approximately a 1 and 2 BMI unit advantage, respectively, over never self-weighers [26,27]. In regard to weight loss, weekly and daily self-weighers lost about 2 to 3 BMI units (~12-18 pounds) more than participants who did not weigh as frequently [26,31]. Based largely on the consistency of the evidence reviewed, frequent self-weighing, at the very least, seems to be a good predictor of moderate weight loss and weight maintenance, both for individuals who have lost weight and are attempting to keep it off and for individuals who are attempting to avoid weight gain in the first place.
Only three studies [28,32,34] directly tested a self-weighing intervention that was not part of an extensive treatment package, relative to control groups that did not receive self-weighing advice or support. These trials were small, showed conflicting results, and raised concerns over internal and external validity. Levitsky and colleagues [28] utilized a brief self-weighing intervention for weight maintenance among female freshman college students (generally non-overweight) and found about 1 BMI unit less weight gain for intervention participants relative to controls. Heckerman, et al. [32] found no significant weight loss advantage for participants enrolled in a 10week behavioral weight loss program that included weekly weigh-ins relative to a group that received the same treatment program without weekly weigh-ins. Attrition was extremely high in this small sample, however, and few conclusions could be drawn from the results. In a somewhat similar approach, Fujimoto et al. [34] also tested a behavioral weight loss program with and without frequent self-weighing. The self-weighing in this study included a recommendation to chart one's weight four times per day. The findings indicated a strong effect in that the self-weighing group lost nearly twice as much weight as compared to the group that did not self-weigh. Analyses from this study, however, were difficult to interpret due to the exclusion of a large part of the randomized sample. As such, selection bias may have been present.
An ideal objective of this review would be to draw conclusions on the optimal dose of self-weighing. At this time, however, the evidence base does not support endorsement of a precise self-weighing frequency and duration that has the most benefit for the most people. In terms of a threshold, weekly self-weighing over several months stands out as what may be the minimum point at which Flow diagram of the study identification, selection, and exclusion process Figure 1 Flow diagram of the study identification, selection, and exclusion process.  [26,27], which were the only ones with enough power to retain a precise assessment of self-weighing frequency across several levels (e.g., daily, weekly, monthly, rarely) versus a dichotomized characterization (e.g., daily, less than daily). These studies found statistically significant benefit, in terms of weight loss, weight maintenance, and weight in general, beginning at weekly self-weighing. It was not clear from any of the reviewed studies if more than daily self-weighing confers added weight benefits.
Perhaps the most significant methodological limitation of the reviewed studies involved the potential for measurement bias. Self-weighing was assessed exclusively by selfreport. In order to prevent recall bias, questionnaire items can not be practically designed to examine self-weighing in a timeframe that extends far beyond the point at which the question is asked. As such, the characterization of selfweighing reported may not accurately reflect self-weighing over the time periods they are deemed to represent. In other words, reported self-weighing frequency at the end of a study may not truly represent the degree to which selfweighing actually occurred over the course of the entire study (or in the months since the last follow-up visit). More objective means of assessing self-weighing frequency, such as scales that record time/date of weigh-ins at home, are needed to validate self-reported measures. Also, the overall demographic profile of study samples was somewhat narrow, primarily involving middle-aged American female volunteers. This seems to be the group most likely to present for weight management services, but it limits generalizations on the effects of self-weighing across the general population.
Although frequent self-weighing was included as part of a treatment package in one large, well-conducted, randomized-controlled trial [30], only three studies were able to experimentally isolate or disaggregate the effects of frequent self-weighing. These studies were small and contained several methodological flaws, however, and therefore strong conclusions could not be drawn. Results from the cross-sectional and prospective cohort studies are also insufficient to make causal claims due to temporality and selection bias issues. Given the controversial endorsement of frequent self-weighing in the scientific community [18,19], it seems timely to experimentally investigate different frequencies and durations of selfweighing in a diverse sample using a large randomizedcontrolled trial. Also, based on the differential associations of self-weighing across different treatment intensities employed by Wing and colleagues [30], the interaction between frequent self-weighing and other weight management program components would be useful for practitioners to better understand. Furthermore, more sensitive analyses are needed to identify the subgroups of people who benefit most from frequent selfweighing. For example, many of the weight maintenance studies reviewed had combined samples of individuals who had lost weight previously and were seeking to prevent weight regain alongside individuals who were normal weight and were seeking to prevent weight gain in the first place. There may be subtle differences in such subgroups that could help practitioners and program designers offer the most appropriate advice.

Conclusion
In balancing the strengths and weaknesses of the evidence reviewed, frequent self-weighing seems to be a helpful strategy for adults who have been successful at losing weight, maintaining weight loss, or preventing weight gain. Furthermore, frequent self-weighing may serve as a useful component of standard weight loss treatment packages. At this time, weekly self-weighing seems to be a reasonable strategy to endorse for adults, but more research is needed to firmly establish the independent causal effect, as well as the optimal dose, both in terms of frequency and duration, of self-weighing. Also, more research needs to be done to determine if self-weighing is more or less effective in specific population subgroups and to identify the potential for psychological risks associated with very frequent self-weighing.