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. Author manuscript; available in PMC: 2023 Apr 1.
Published in final edited form as: J Contextual Behav Sci. 2022 Mar 23;24:60–64. doi: 10.1016/j.jcbs.2022.03.008

The Relation of Grit to Weight Loss Maintenance Outcomes

Christine C Call a,b,*, Laura D’Adamo a,c, Nicole T Crane a, Charlotte J Hagerman a, Meghan L Butryn a
PMCID: PMC9053131  NIHMSID: NIHMS1792994  PMID: 35496324

Abstract

Biological, genetic, and environmental factors make weight loss very difficult. Acceptance-based behavioral treatment (ABT) supplements standard behavioral treatments (BT) for obesity by teaching skills to accept the discomfort inherent to weight control behaviors and prioritize long-term, values-based goals. Grit, the ability to persevere in goal pursuit, overlaps conceptually with ABT principles and may predict outcomes in ABT. During a randomized controlled trial comparing three weight loss interventions (BT, BT with an emphasis on physical activity [BT+PA], ABT with an emphasis on physical activity [ABT+PA]), this study examined if grit predicted weight loss, intervention engagement (session attendance and dietary self-monitoring), and perceived intervention effectiveness, and whether intervention condition moderated these relationships. Participants (N=309) with overweight/obesity enrolled in an 18-month weight loss intervention completed the Short Grit Scale at baseline. Weight and PA were measured at baseline, during the intervention (12 and 18 months), and at follow-up (24 and 36 months). Session attendance and dietary self-monitoring were assessed throughout the intervention, and perceived intervention effectiveness at end-of-intervention. The relation of grit to several outcomes depended on condition. In ABT+PA, but not BT or BT+PA, lower grit related to higher weight loss at 12 and 24 months, session attendance, and perceived intervention effectiveness. Grit was not related to PA or dietary self-monitoring in any condition. ABT’s focus on building skills to facilitate long-term goal pursuit may be unique and beneficial to those with lower grit. Those with higher grit may already possess ABT-consistent skills and benefit less from ABT. Research on trait-level characteristics like grit in relation to weight must be cautious not to reinforce weight bias; rather, this work suggests that an evidence-based intervention (ABT) may be well-suited to those with lower grit levels seeking weight loss.

Keywords: grit, obesity, behavioral weight loss, weight loss maintenance, acceptance and commitment therapy

Over the past decade, acceptance-based approaches to behavioral weight loss have emerged as an evidence-based treatment option for obesity (Butryn et al., 2019). One prominent model developed by Forman and Butryn (2015), referred to as acceptance-based behavioral treatment (ABT), integrates content and strategies from acceptance and commitment therapy (ACT; Hayes et al., 2009) into more traditional behavioral weight loss treatment (i.e., BT). The overarching goal of ABT remains consistent with standard BT: to achieve a weight loss of 5–10% of initial body weight, an amount associated with significant health benefits (Butryn et al., 2011). However, ABT introduces additional psychological and behavioral tools to achieve this goal. The premise of ABT is that in the modern environment, evolutionarily-programmed biological drives to conserve energy and consume palatable foods make it difficult to adhere to weight control prescriptions (Forman & Butryn, 2015). The ABT model validates that difficulty with losing weight is not a failure of motivation or effort. In fact, most treatment-seeking adults with obesity have previously lost, and subsequently regained, significant weight through prior weight loss efforts (Latner & Ciao, 2014; Marchesini et al., 2004). Rather, biologically-driven responses to powerful internal (e.g., emotional, cognitive) and environmental cues promoting overeating and inactivity eventually overwhelm self-regulatory abilities, making long-term weight loss challenging (Forman & Butryn, 2015). As such, traditional behavioral skills such as goal-setting and self-monitoring of weight, food intake, and physical activity (PA) are seen as a necessary but insufficient foundation for adopting long-term changes to eating behavior and PA. Therefore, in addition to behavioral content, ABT sessions focus on the ACT-consistent skill of prioritization of long-term goals and values over immediate pleasure (Forman & Butryn, 2016). Participants are taught to cultivate mindful awareness of uncomfortable internal experiences (e.g., food cravings, urges to engage in sedentary behaviors), accept these uncomfortable experiences for what they are, and develop willingness to persist in values-consistent weight control behaviors despite discomfort (Butryn et al., 2019). ABT validates that there are a multitude of factors that make weight loss exceedingly challenging, including biological, genetic, and environmental factors, while also instilling self-efficacy in participants that changing their psychological and behavioral approach to weight control will help them achieve weight loss. A key next step in obesity research is to identify whether certain participants fare better in the traditional vs. acceptance-based versions of behavioral weight loss treatments (i.e., BT vs. ABT) to inform treatment matching.

Grit, a personality trait defined as the ability to sustain commitment toward long-term goals despite challenges (Duckworth & Quinn, 2009), is a compelling construct to consider for treatment matching in weight loss based on its conceptual overlap with ABT principles. Individuals with high levels of grit are theorized to persevere in long-term goal pursuit in the face of obstacles. As such, they may already have mastery of some key skills that ABT attempts to facilitate, such as willingness to persist in values-consistent action despite internal discomfort or loss of immediate pleasure. These participants may benefit less from ABT as it may not offer them novel skills. Participants with lower levels of grit may have greater potential to benefit from ABT content, which may improve weight loss outcomes. No peer-reviewed research has examined how grit relates to success in behavioral weight loss treatments, nor whether the association of grit with weight control outcomes depends on the type of treatment delivered. However, data from related areas of research provide empirical precedence for examining the role of grit in weight loss treatment. The most relevant data available are from a year-long weight gain prevention trial focused on nutrition education for premenopausal women with mean body mass index (BMI) in the overweight range, which found that higher baseline grit predicted lower weight and BMI at the end of the program (Metzgar & Nickols-Richardson, 2016). Cross-sectional studies of non-treatment seeking adults also suggest that grit is associated with weight control behaviors, such as more PA (Reed et al., 2013) and healthier eating (Totosy de Zepetnek et al., 2021).

Research on characteristics such as grit in the context of weight loss treatment must be cautious about reinforcing inaccurate and harmful stereotypes about obesity. If participants with lower levels of grit experience smaller weight losses, this does not imply a failure on the part of the individual. Rather, such a finding has important implications for identifying intervention targets to support weight loss efforts (e.g., skills to build grit). Similarly, if individuals with lower grit fare better or worse in certain interventions, assessing grit prior to treatment could allow these individuals to receive treatment that is well-matched to their needs. On the other hand, if grit is not associated with better treatment outcomes, such a finding could bolster evidence refuting inaccurate stereotypes about obesity as a failure of self-control or self-discipline, which contribute to harmful weight bias (Brewis, 2011; Puhl & Brownell, 2003).

The present study explored if baseline grit was associated with success in a weight control trial comparing standard BT, BT with a focus on PA (BT+PA), and ABT with a focus on PA (ABT+PA) (Butryn et al., 2021)). Specifically, we examined if grit predicted weight loss, intervention engagement (PA, completion and quality of dietary self-monitoring, intervention attendance), and perceived intervention effectiveness, and whether condition moderated these relationships.

Method

This study was a secondary analysis of a pre-registered randomized controlled trial comparing three weight loss maintenance interventions (Clinicaltrials.gov identifier NCT02363010).

Details of the trial not reported here, including a participant flow chart, can be found in the main outcomes paper (Butryn et al., 2021). Data and code for statistical analyses are available by reasonable request to the authors.

Participants

Participants in the parent study (N = 320) were adults (aged 18–70 years) from the community with a BMI of 27–45 kg/m2. Exclusion criteria included: medical/psychiatric conditions that could pose a risk or interfere with study participation; history of bariatric surgery; use of weight-affecting medication; weight loss of ≥5% in the past 6 months; pregnancy or plans to become pregnant during the trial; participation in another weight loss program; or having an immediate family or household member in the study. This secondary analysis only included participants who completed the Grit-S scale at baseline (N = 309).

Procedure

Participants received 6 months (16 group sessions) of standard BT to induce weight loss, followed by 12 months (14 group sessions sessions) of maintenance treatment. Participants were randomized to one of three conditions for the maintenance phase: continued standard BT, BT+PA, or ABT+PA. This secondary analysis examined data from baseline (pre-intervention), 12-months (i.e., halfway through the randomized weight loss maintenance intervention), 18 months (i.e., end of the randomized weight loss maintenance intervention), and two follow-up timepoints (24 and 36 months). Informed consent was collected; the Drexel University Institutional Review Board approved this study Institutional Review Board approved this study.

Measures

At baseline, participants self-reported sex, age, racial identity, ethnicity, and level of education and completed the Short Grit Scale (Grit-S), an 8-item measure with a possible range of 1 (not at all gritty) to 5 (extremely gritty; Duckworth & Quinn, 2009). To assess percent weight loss (i.e., total weight loss from baseline to each assessment point as a percentage of baseline weight), research staff measured participants’ height (using a stadiometer) and weight (using a Tanita® model WB-3000 digital scale), with participants in street clothes and without shoes. Measurements were taken in duplicate and averaged. To measure moderate-to-vigorous PA (MVPA) at each timepoint, participants were provided ActiGraph (Pensacola, FL) GT3X tri-axial, solid state accelerometers and instructed to wear them for all waking hours for 7 days. Data were included if the accelerometer was worn for ≥10 hours each day for ≥ 4 days. Participants monitored their daily dietary intake via electronic or pen-and-paper food records based on their preference. Assessors collected 14-day food records twice during the weight loss maintenance intervention (sessions 20 and 26) and coded them for food record completion and quality as described by Rosenbaum et al. (2018). Session attendance during the 14-session weight loss maintenance intervention was tracked and summed. At end-of-treatment (18 months), participants reported perceived intervention effectiveness (“How effective was this program in helping you lose weight?”) on a 1–5 scale, with higher scores indicating greater perceived effectiveness.

Statistical Analysis Plan

Analyses were conducted in SPSS v. 26 (IBM Corp., 2018). Multiple imputation was performed using MCMC algorithms known as chained equations imputation (Yuan, 2010) to handle missing data. Data were inspected for normality and adherence to assumptions. Two dummy variables were created to compare the ABT+PA treatment condition (reference group) to the BT and BT+PA treatment conditions, respectively (i.e., ABT+PA vs. BT and ABT+PA vs. BT+PA). OLS regression analyses examined the main effect of grit, the main effects of the two treatment dummy variables, and the interaction of grit with each of the treatment dummy variables, accounting for covariates, on percent weight loss and minutes/week of MVPA at 12, 18, 24, and 36 months; ratings of food record quality and completion at sessions 20 and 26; attendance at the 14 weight loss maintenance sessions; and perceived intervention effectiveness at end-of-treatment (18 months). For any significant interactions, simple slopes analyses were performed. Analyses controlled for the baseline version of the outcome variable where appropriate (e.g., when percent weight loss was the outcome, baseline weight was entered into the model as a covariate). Level of education was also included as a covariate in all analyses because participants with a graduate or professional degree in this sample had significantly higher grit scores than those with lower educational levels, consistent with prior research and theory (Duckworth et al., 2007); other demographic variables were not related to baseline grit, nor were they theorized to, and were therefore not included in models.

Results

In this sample (N = 309; 78.3% female; 70.2% White; 95.8% non-Hispanic; 77.4% Bachelor’s degree of higher; MAge = 52.68 ± 10.40 years; MBMI = 35.14 ± 4.76 kg/m2), mean grit was 3.21 (SD = 0.24; sample range: 2.50–3.86). As shown in Table 1, there was no main effect of grit at any timepoint on percent weight loss, minutes/week of MVPA, food record completion or quality, or perceived intervention effectiveness. Higher grit was significantly related to lower session attendance in the 14 weight loss maintenance sessions from 6–18 months. The interaction effects of grit by intervention condition (for both dummy variables) were significant for percent weight loss at 12 and 24 months (not at 18 or 36 months), session attendance, and perceived intervention effectiveness (see Table 1). Specifically, lower grit was associated with greater weight loss, session attendance, and perceived intervention effectiveness in the ABT+PA condition, but not in the BT or BT+PA conditions (see Figure 1). The interactions of grit by intervention condition on MVPA and food record quality and completion were not significant.

Table 1.

Results of OLS Regression Analyses examining the main effects of grit and the interaction effects of grit * condition on outcomes

Predictor
Grit (Main Effect) Grit * (BT vs. ABT+PA) Grit * (BT+PA vs. ABT+PA)
Outcome1 B (SE) p B (SE) p B (SE) p
Percent Weight Loss2
 12 months 3.22 (2.33) .17 −10.90 (5.54) .05* −14.73 (5.72) .01*
 18 months −.72 (3.23) .82 −8.29 (7.61) .28 −9.16 (7.80) .24
 24 months 1.06 (3.01) .73 −14.07 (7.07) .05* −15.87 (6.40) .01*
 36 months .09 (2.80) .48 −10.18 (7.28) .17 −9.77 (6.71) .15
MVPA (minutes/week)2
 12 months 25.13 (29.51) .85 −45.87 (69.47) .51 55.55 (72.94) .45
 18 months −8.82 (29.00) .81 −113.08 (67.65) .10 65.95 (70.94) .35
 24 months −7.42 (27.91) .79 −116.32 (65.31) .08 −9.14 (68.74) .89
 36 months 30.26 (26.24) .25 −30.31 (61.45) .62 96.36 (64.62) .14
Food record completion2, 3
 Session 20 −.15 (.11) .16 .14 (.26) .58 −.29 (.26) .27
 Session 26 −.08 (.12) .53 .31 (.31) .30 .32 (.32) .32
Food record quality2, 3
 Session 20 −.09 (.09) .35 .26 (.23) .26 −.03 (.23) .90
 Session 26 −.10 (.11) .34 .24 (.27) .38 .13 (.28) .64
Attendance at sessions 17–30 −2.25 (1.13) .05* 7.13 (2.61) .006** 6.59 (2.75) .02*
Perceived treatment effectiveness4 .14 (.31) .65 2.24 (.75) .003** 2.27 (.74) .002**
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Note.

1

All analyses controlled for intervention condition and level of education.

2

The indicated analyses controlled for the baseline version of the outcome variable.

3

Food record completion and quality were rated on a 1–7 scale; higher values indicate better completion/quality.

4

Perceived treatment effectiveness was rated on a 1–5 scale; higher values indicate greater perceived effectiveness

*

p<.05

**

p<.005

Figure 1. Significant Interaction Effects of Grit * Intervention Condition.

Figure 1

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Note. Panel A: Lower grit was associated with greater percent weight loss in ABT+PA (b = 12.01, p = .002) but not BT (b = 1.11, p = .75) or BT+PA (b = −2.72, p = .47). Panel B: Lower grit was associated with greater session attendance in ABT+PA (b = −7.0, p < .001) but not BT (b = .13, p = .94) or BT+PA (b = −.41 , p = .83). Panel C: Lower grit was associated with greater perceived intervention effectiveness in ABT+PA (b = −1.51, p = .006) but not BT (b = .74, p = .16) or BT+PA (b = .84, p = .10).

Discussion

The present study examined the relation of grit, the perseverance to sustain efforts toward goals over time (Duckworth & Quinn, 2009), to weight control success. There was no main effect of grit on any outcome except session attendance, such that participants with lower grit had greater session attendance when conditions were collapsed. It is possible that these participants, who may struggle to persevere in long-term goal pursuit, especially benefited from the support and accountability of sessions and thus attended them more frequently than those with high grit. Those with higher levels of grit may benefit less from sessions and therefore attend fewer, particularly given that they might have prior experience engaging in some of the behaviors necessary for weight control success. Indeed, in cross-sectional non-treatment-seeking community samples, higher grit is associated with lower body mass index (BMI; Thomas et al., 2015), more PA (Reed et al., 2013), and healthier eating (Totosy de Zepetnek et al., 2021).

Analyses also revealed that the relation of grit to some outcomes depended on intervention condition. In ABT+PA, but not in the other conditions, lower grit was related to greater weight loss at certain timepoints, more frequent session attendance, and greater perceived intervention effectiveness. Results suggest that ABT may be particularly effective for individuals with lower grit. ABT’s emphasis on accepting discomfort in the service of long-term goals may offer these participants novel skills that they have not yet incorporated into weight loss attempts. Individuals with higher grit may already possess ABT-consistent skills and therefore find ABT less helpful and engage less in the intervention. Because grit was only assessed at baseline, it is unknown if grit changed over time in any condition or if such changes help to explain why individuals with lower baseline grit fared better than those with higher baseline grit in ABT. Future work could examine these questions. One unpublished study (Smith, 2018) previously examined grit in a weight loss trial that randomized participants to standard BT or ABT. Consistent with the present study’s null results, baseline grit was not associated with weight loss or change in body fat during the intervention when the two conditions were collapsed. Unlike the current study, Smith (2018) found no interaction of grit and condition in predicting outcomes, but those analyses were underpowered.

Many people attribute poor weight control to maladaptive trait-level characteristics such as lack of willpower (Puhl & Heuer, 2009), which is associated with internalized weight bias (Pearl & Lebowitz, 2014). The results from the current study are consistent with the notion that successful weight regulation involves a complex mix of genetic, biological, environmental, social, and psychological factors (Montesi et al., 2016; Schwartz et al., 2017). It may reduce internalized stigma for individuals in obesity treatment to learn that if they struggle to achieve weight loss, it is not likely attributable to a low level of grit. Furthermore, it appears that an evidence-based intervention for weight loss, ABT, may help those with lower levels of grit achieve weight loss goals.

This study had several strengths, including examining long-term weight outcomes and investigating several measures of treatment adherence/engagement. However, the sample was largely female, non-Hispanic, White, and highly educated, which limits generalizability. Results also may not generalize to other acceptance-based approaches for obesity, some of which differ substantially from the ABT model developed by Forman and Butryn (2015) that was utilized in this study. For example, Berman et al. (2016) developed an acceptance-based intervention for women with obesity and depression that does not include weight loss as a stated goal but instead aims to foster acceptance of participants’ bodies and moods and to broadly increase values-consistent behaviors. Grit may function differently in acceptance-based programs with different intervention targets and approaches. Overall, findings suggest that success in weight control programs is not attributable to grit, but that ABT+PA may be especially beneficial for those with lower baseline grit. Future research should attempt to replicate these results in samples with greater demographic diversity.

Highlights.

  • We examined grit, perseverance in long-term goal pursuit, in obesity treatments

  • Grit predicted outcomes in acceptance-based behavioral treatment (ABT) for obesity

  • Lower levels of grit related to greater 12- and 24-month weight losses in ABT

  • Lower levels of grit related to greater perceived intervention effectiveness in ABT

  • Lower levels of grit related to greater session attendance in ABT

Funding:

The parent study (Trial registration: ClinicalTrials.gov Identifier NCT02363010) was funded by National Institute of Diabetes and Digestive and Kidney Diseases Grant R01 DK100345 (PI: Meghan L. Butryn). This work was also supported, in part, by National Institute of Mental Health Grant T32 MH018269 (PI: Michele D. Levine; Fellow; Christine C. Call).

Footnotes

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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