Psychosocial Outcomes of the Fast Track to Health Clinical Trial in Adolescents with Obesity

Abstract

Introduction

Adolescent obesity requires effective and accessible treatment. Intensive dietary interventions may be used as adjunctive therapy to behavioral interventions and lead to weight loss. The effects of behavioral interventions on psychosocial outcomes are mixed, and the impact of intensive interventions with shifts away from normal eating habits and social norms is not clear.

Methods

Adolescents (13–17 years) with obesity and ≥1 complication participated in a 52-week RCT, conducted 2018–2023 (ACTRN12617001630303). The intervention compared a 4-week very low energy diet followed by intermittent or continuous energy restriction (48 weeks). Anthropometry and psychosocial health were assessed at baseline, weeks 4, 16, and 52 including Dutch Eating Behaviour Questionnaire (DEBQ), Rosenberg Self-Esteem Scale (RSE), Weight Bias Internalization Scale (WBIS), Body Appreciation Scale (BAS), and Depression Anxiety and Stress Scale (DASS). Intention-to-treat analysis using linear mixed models investigated changes over time between intervention groups.

Results

In total, 141 adolescents (70 female) were enrolled and 97 (48 female) completed the intervention. There were significant reductions in external eating (DEBQ, p < 0.001), weight bias internalization (WBIS, p < 0.001), anxiety (DASS, p < 0.001), and stress (DASS, p = 0.082) and significant increases in self-esteem (RSE, p < 0.001) and body appreciation (BAS, p < 0.001) in both groups. There were increases in dietary restraint (DEBQ, p = 0.595) and decreases in emotional eating (DEBQ, p = 0.645) and depression (DASS, p = 0.381) which returned to baseline by the end of intervention. Reductions in BMI z-score were significantly associated with improvements in emotional eating (r = 0.215, p = 0.046, n = 87) and body appreciation (r = −0.235, p = 0.027, n = 88).

Conclusion

Intensive interventions incorporating dietary and behavioral components were associated with improvements in psychosocial health among adolescents with obesity-associated complication.

Introduction

Adolescent obesity requires effective and accessible treatment [1]. Intensive dietary interventions such as very low energy diets (VLEDs) or intermittent energy restriction (IER) have potential to be used as adjunctive therapy to intensive behavioral interventions [2]. The Fast Track to Health trial compared the effectiveness of IER with continuous energy restriction (CER) in adolescents with obesity and associated complications [3]. The trial found a reduction in body mass index (BMI), expressed as a percentage of the 95th percentile for age and sex, in both groups, with no difference between groups. Improvements in blood pressure percentile, total cholesterol, triglycerides, and symptoms of depression and eating disorders were also reported [4, 5].

Adolescents with obesity may experience negative impacts across several domains of psychosocial health. They may have reduced body image and self-esteem and poorer quality of life and are more likely to engage in disordered eating behaviors compared to their lower weight peers [6]. Further, adolescents with high BMI are likely to have higher internalized weight bias compared to those with BMI less than 25 kg/m², which is further associated with poorer psychosocial health outcomes [7]. International guidelines acknowledge the importance of considering psychosocial health in pediatric obesity prevention and treatment [8, 9]. In addition, guidelines recommend weight bias and stigma are directly addressed, by understanding and acknowledging the complex genetic and environmental factors that contribute to obesity [8, 10].

Systematic reviews have examined the change in self-esteem, body image, depression, anxiety, and quality of life during behavioral interventions for adolescents with obesity [11–15]. Such interventions are typically structured, multicomponent, and professionally led; and outcomes tend to improve or do not worsen. However, few interventions using intensive dietary approaches have been included in these reviews. Intensive dietary approaches may involve a more dramatic shift away from normal eating habits and social norms compared to providing dietary counseling as part of behavioral interventions [2] and thus warrant further investigation. Our team has previously reported improvements in eating disorder and depression symptoms following intensive dietary interventions, yet the broader impact of behavioral interventions on less studied psychosocial outcomes that impact the lives of adolescents has yet to be investigated. Further, there is limited literature exploring changes in internalized weight bias in pediatric obesity treatments settings [7, 16]. Thus, the aim of this study was to assess the change in domains of psychosocial health during the Fast Track to Health trial including eating behaviors, self-esteem, weight bias internalization, body appreciation, depression, anxiety, and stress.

Methods

Study Design

Fast Track to Health was a multisite randomized controlled trial conducted in two tertiary-level hospitals in Australia between 2018 and 2023. The trial was approved by the Sydney Children’s Hospitals Network Human Research Ethics Committee (HREC/17/SCHN/164), registered at Australian and New Zealand Clinical Trials Registry (ACTRN12617001630303), and detailed methods are published [3] and are described briefly. Participants underwent a 52-week intensive behavioral intervention [5] and were randomly allocated to one of two intervention groups using a computer-generated randomization schedule (1:1). A CONSORT checklist is provided in online supplementary Table 1 (for all online suppl. material, see https://doi.org/10.1159/000551890).

Participants

Adolescents aged 13–17 years with at least one obesity-associated cardiometabolic complication were recruited. Participants were screened and monitored for depression and eating disorders at baseline and weeks 4, 16, and 52. Significant medical or psychiatric illness were exclusion criteria and adolescent meeting prespecified cut points on validated screening tools were reviewed by a clinical psychologist or pediatrician. Agreement to participate was obtained from adolescents and written consent from parents/carers. Demographic, weight, and cardiometabolic outcomes are published [5], as have findings from depression and eating disorder screening and monitoring processes [4].

Interventions

Following randomization, participants followed a VLED for 4 weeks, then either IER or CER until 52 weeks. Interventions were based on clinical practice and previous clinical trials [17, 18] and were documented in an intervention standard operating procedure framework [3]. The intervention was delivered by trained study dietitians, with 13 face-to-face visits and nine additional support contacts (via text, email, or telehealth) over the 52 weeks. Clinical consultations with trained pediatricians were conducted at baseline and week 16 [19]. The clinical psychologist reviewed depression and eating disorder screening surveys [4], discussed issues with study dietitians and pediatricians, and assessed participants identified as “at risk” by study clinicians or screening/monitoring surveys. Consultations used a motivational “coaching” model, implementing techniques from cognitive behavior therapy on an individual basis [3].

The VLED phase provided ∼800 kcal/d and participants were provided with micronutrient-complete meal replacements (Optifast^®VLCD™, Nestlé Health Science, Nestlé Australia Ltd). Each week, the IER dietary plan consisted of three reduced energy days (600–700 kcal/d) and 4 days of healthy eating with no energy restriction. The CER dietary plan provided an energy prescription based on age (13–14 years: 1,400–1,650 kcal; 15–17 years: 1,650–1,900 kcal) with high fiber (>30 g/d) and moderate carbohydrate (40–50% energy) and protein (20–25% energy).

Outcomes

Outcomes were predefined and assessed at baseline and weeks 4, 16 and 52. Anthropometric measurements were collected by a trained assessor blinded to treatment allocation. Psychosocial outcomes were assessed using validated tools administered by an online survey platform hosted by the University of Sydney (REDCap [20, 21]), including Dutch Eating Behaviour Questionnaire (DEBQ, subscale scores 0–5) [22]; Rosenberg Self-Esteem Scale (RSE, scores 10–40) [23]; Weight Bias Internalization Scale (WBIS, scores 1–7) [24]; the Body Appreciation Scale (BAS, scores 1–5) [25]; and Depression Anxiety Stress Scale 21-items (DASS-21, subscale scores 0–42) [26]. The DASS-21 was introduced following trial commencement on 27 May 2019 (see online supplementary Table 2 for further details describing psychosocial outcomes).

Analysis

Statistical analysis was exploratory and conducted according to a prespecified plan using SPSS Statistics, version 28.0 (IBM Inc.). All participant data were retained. Linear mixed models (LMM) were used to estimate the change in outcomes at baseline, week 4, week 16, and week 52 consistent with intention-to-treat for longitudinal analysis. An autoregressive first-order covariance structure and restricted maximum likelihood were used to estimate the change in outcomes between baseline, weeks 4, 16, and 52. Time (baseline, weeks 4, 16, and 52) was entered as a fixed (categorical) variable. Baseline was assumed to be equal across groups. The mixed models procedure accounted for within-participant correlations and missing data points. A time by group interaction was included to investigate whether rates of change in outcomes were different between groups. Data were log-transformed when not normally distributed to meet assumptions of LMM (depression scale only). Assumptions of modeling were met, and results are presented as the difference in estimated marginal means (EMM). A post hoc pairwise comparison was conducted to compare means over time. Independent sample t tests and Mann-Whitney U tests were used to test for differences in outcomes at baseline, weeks 4 and 16 between completers and non-completers. Spearman’s rank correlation was computed to assess the relationship between percent change in psychosocial outcomes and change in BMI z-score (BMIz) and BMI expressed as a percentage of the 95th percentile (BMI95). No adjustments were made for multiple comparisons.

Results

In total, 141 (70 female) adolescents were recruited and 97 (48 female) completed the 52-week intervention (see online suppl. Figure 1). At baseline, adolescents had a mean (SD) BMI of 35.39 kg/m² (4.17) and a BMIz of 2.40 (0.46) (Table 1). Adolescents had median (IQR) scores of 2.50 (1.20) on the DEBQ restraint subscale, 2.00 (1.51) on DEBQ emotional eating subscale, 2.75 (1.10) on DEBQ external eating subscale, 29.00 (6.50) on RSE, 4.00 (9.33) on DASS depression subscale, 6.00 (10.00) on DASS anxiety subscale, 6.00 (10.00) on DASS stress subscale, 3.11 (1.13) on BAS, and 3.91 (1.77) on WBIS. Completers of the study had lower median (IQR) scores on the DASS stress subscale at baseline (completers 4.3 [10.0], non-completers 12.0 [12.0], p = 0.042) and higher median (IQR) scores on the RSE at week 16 (completers 30.0 [9.0], non-completers 28.5 [9.25], p = 0.023). There were no differences in any other outcomes between completers and non-completers at any time point.

Table 1.

Baseline characteristics

​	All participants (n = 141)	IER (n = 71)	CER (n = 70)
Age, median [range], years	14.8 [12.9–17.9]	14.8 [12.9–17.9]	14.8 [12.9–17.8]
Sex, female, n (%)	70 (49.6)	36 (50.7)	34 (48.6)
Anthropometry, mean (SD), n (%)
Weight, kg	100.42 (16.50)	97.71 (15.09)	103.09 (17.61)
BMI, %95th centile	130 (15)	128 (14)	132 (16)
Waist to height ratio ≥ 0.5	139 (98.6)	70 (98.6)	69 (98.6)

Eating Behaviors

Figure 1 shows changes over time for both groups. Dietary restraint (DEBQ) transiently increased over time (LMM, F = 3.05, p = 0.029), with no significant differences between groups (LMM, F = 1.18, p = 0.317). There were no differences at week 52 compared to baseline in either group (p = 0.595, see online suppl. Table 3). Post hoc comparisons indicated that there was a significant increase at week 4 (EMM [95% CI] = 0.211 [0.399 to 0.022]) and −16 (0.343 [0.581 to 0.105]) in the IER group. There was no significant association between percent change in restraint (DEBQ) at week 52 and change in BMIz (r = −0.091, p = 0.404, n = 87) and BMI95 (r = −0.081, p = 0.456, n = 87).

Fig. 1.

Change between baseline and week 52 in dietary restraint (a), emotional eating (b), external eating (c). IER, intermittent energy restriction; CER, continuous energy restriction; EMM, estimated marginal means; DEBQ, Dutch Eating Behavior Questionnaire.

Emotional eating (DEBQ) significantly changed over time (LMM, F = 2.914, p = 0.034), with no significant differences between groups (LMM, F = 2.579, p = 0.054). There was a significant decrease in emotional eating (DEBQ) at week 4 (EMM [95% CI] = −0.206 [−0.039 to −0.373]) in the IER group and at week 16 (−0.293 [−0.073 to −0.513]) in the CER group. However, by week 52, there were no differences compared to baseline in either group (p = 0.645). The percent change in emotional eating (DEBQ) at week 52 was significantly related to change in BMIz (r = 0.215, p = 0.046, n = 87) and BMI95 (r = 0.228, p = 0.033, n = 87), indicating reduced emotional eating with increased weight loss.

External eating (DEBQ) was significantly different between groups, over time (LMM, F = 5.681, p < 0.001). Post hoc comparisons indicated that the IER group had reductions in external eating during VLED phase, which remained reduced after the commencement of IER up to 52 weeks. The CER group had no change in external eating during VLED phase, but a significant reduction following transition to the CER intervention, which remained until 52 weeks (Fig. 1, c). There were no differences between groups at week 52 (p = 0.942). There was no significant association between percent change in external eating (DEBQ) at week 52 and change in BMIz (r = 0.170, p = 0.114, n = 87) and BMI95 (r = 0.194, p = 0.072, n = 87).

Self-Esteem, Weight Bias, and Body Appreciation

Figure 2 shows self-esteem (RSE) significantly increased over time (LMM, F = 11.014, p < 0.001), with no significant differences between groups (LMM, F = 1.445, p = 0.229). Post hoc comparisons indicated both groups increased self-esteem at week 4 (p < 0.001) and remained significantly higher than baseline until week 52. There was no significant association between percent change in self-esteem (RSE) at week 52 and change in BMIz (r = −0.015, p = 0.893, n = 88) or BMI95 (r = −0.012, p = 0.908, n = 88).

Fig. 2.

Change between baseline and week 52 in self-esteem (a), weight bias internalization (b), body appreciation (c). IER, intermittent energy restriction; CER, continuous energy restriction; EMM, estimated marginal means; RSE, Rosenberg Self-Esteem Scale; WBIS, Weight Bias Internalization Scale; BAS, Body Appreciation Scale.

Weight bias internalization (WBIS) significantly decreased over time in both groups (LMM, F = 10.143, p < 0.001), with no significant differences between groups (LMM, F = 1.145, p = 0.331). The percent change in WBIS at week 52 was not associated with change in BMIz (r = 0.191, p = 0.075, n = 88) or BMI95 (r = 0.195, p = 0.069, n = 88). Body Appreciation Scale (BAS) significantly increased over time in both groups (LMM, F = 6.685, p < 0.001), with no significant differences between groups (LMM, F = 0.816, p = 0.486). The percent change in BAS at week 52 was inversely related to change in BMIz (r = −0.235, p = 0.027, n = 88) and BMI95 (r = −0.253, p = 0.017, n = 88), indicating body appreciation increased as adolescents lost weight.

Depression, Anxiety, and Stress

Depression (DASS) transiently decreased in both groups (LMM, F = 19.192, p < 0.001); however, there were significant differences between groups (LMM, F = 2.945, p = 0.034). Post hoc comparisons indicated that there were significant decreases compared to baseline at week 4 (EMM [95% CI] = −2.584 [−4.347 to −0.822]) and week 16 (−4.053 [−6.263 to −1.844]) in the IER group and at week 4 (−4.158 [−5.907 to −2.409]) and week 16 (−3.088 [−38 to −0.938]) in the CER group (see Figure 3). However, there were no differences at week 52 compared to baseline in either group (p = 0.381). There was no significant association between percent change in depression (DASS) at week 52 and change in BMIz (r = 0.155, p = 0.334, n = 41) and BMI95 (r = 0.153, p = 0.341, n = 41).

Fig. 3.

Change between baseline and week 52 in depression* (a), anxiety (b), stress (c). IER, intermittent energy restriction; CER, continuous energy restriction; EMM, estimated marginal means; DASS, Depression, Anxiety and Stress Scale. *Depression data shown are untransformed; transformations were applied only for statistical analyses.

Anxiety (DASS) significantly decreased over time in both groups (LMM, F = 12.027, p < 0.001), with no significant differences between groups (LMM, F = 1.869, p = 0.136). There was no significant association between percent change in anxiety (DASS) at week 52 and change in BMIz (r = −0.096, p = 0.529, n = 45) and BMI95 (r = −0.096, p = 0.533, n = 45). Stress (DASS) significantly decreased over time in both groups (LMM, F = 19.518, p < 0.001), with no significant differences between groups over time (LMM, F = 0.308, p = 0.082). There was no significant association between percent change in stress (DASS) at week 52 and change in BMIz (r = −0.171, p = 0.260, n = 45) and BMI95 (r = −0.139, p = 0.363, n = 45).

Discussion

This study aimed to examine the change across several domains of psychosocial health during the Fast Track to Health trial. At the end of the intervention, there were significant reductions in external eating, weight bias internalization, anxiety, and stress, and significant increases in self-esteem and body appreciation in both groups. Dietary restraint, emotional eating and depression were unchanged at the end of the intervention in both groups. Emotional eating reduced and body appreciation increased as adolescents lost weight. There were generally no differences between groups for most outcomes. This suggests that the psychosocial health impacts of behavioral interventions may be unrelated to the type of diets implemented. Indeed, the support provided as part of these multidisciplinary interventions likely had the most impact on psychosocial health. Together with results showing improved markers of physical health [5], this study shows the potential dual role of intensive behavioral interventions on improving both physical and psychosocial health.

Earlier systematic reviews have reported general improvements in some measures of psychosocial health following adolescent obesity interventions, including depression, anxiety, self-esteem, and quality of life [11–14]. However these reviews generally included less restrictive dietary interventions. A 2019 review of VLEDs found two studies reporting on psychosocial outcomes in adolescents, with either improvements or no change following the interventions [27], which is consistent with adult literature [28]. Further, similar improvements are observed in psychosocial health following metabolic or bariatric surgery in adolescents [29, 30]. Thus the improvements in external eating, self-esteem, weight bias internalization, body appreciation, anxiety, and stress are not surprising findings. Importantly, many of these improvements were unrelated to weight loss. This is consistent with literature from adult studies showing weight bias internalization is unrelated to weight loss [16]. However, body appreciation improved with weight loss, which is consistent with reviews in adolescents showing improved body image is associated with weight loss [11]. This trial, as with existing literature on psychosocial outcomes, focuses on within-person changes in psychosocial health. Intensive health behavior interventions may impact the broader social environment of an adolescent’s life, including peer and family relationships, and further research is needed to understand these influences [31]. Indeed, adolescents and caregivers are interested in general health improvements, beyond weight loss success [32]. Adolescents with obesity most commonly define success of an intervention as feeling better about themselves, followed by having more energy and generally feeling healthier [32]. Longer term follow-up is needed to determine longevity of these effects, particularly for outcomes not related to weight change.

The observed improvements in psychosocial health may be related to the support delivered as part of the Fast Track to Health study. The intensive behavioral support likely exceeds the level of care typically available via routine clinical practice in Australia. Participants were scheduled to connect with the dietitian 22 times over 12 months, with 13 face-to-face visits. Pediatricians conducted clinical assessments at baseline and week 16. Further, a subgroup of adolescents accessed additional medical, dietetic, and psychological support throughout the intervention [19]. This extra support may have contributed to positive outcomes, for example, in community samples, compassion received from others improves girls’ body appreciation [33]. The clinicians were experienced in tertiary-level obesity treatment, meaning adolescents and their families were accessing specialized care not typically available to young people affected by obesity. Indeed, in findings from a global cross-sectional survey of 5,275 adolescents with obesity, only 13% reported seeing an obesity or weight management doctor in the past year [32]. The dose of contact hours during behavioral interventions is related to improved weight and metabolic outcomes [34, 35], leading the 2023 American Academy of Pediatrics clinical practice guideline to recommend a minimum of 26 contact hours [8]. The findings from this study further emphasize the importance of engaging adolescents in intensive, professionally led behavioral interventions to improve physical health and promote psychosocial health. Thus, there is a need to ensure appropriate access to specialized services, with health professionals appropriately trained in clinical obesity care for adolescents.

This study demonstrated significant changes in eating behaviors of adolescents. This is consistent with previous systematic reviews which report improvements in eating behaviors for children and adolescents undergoing weight management [13, 36, 37]. These changes are often assessed only in the short term [36] and are likely related to content and support provided by dietitians or other health professionals. Further data are needed to assess whether these changes are sustained in the long term. Dietary strategies to support interventions in Fast Track, included individualized meal plans, support for family meals, eating out with friends, and enjoying special events. Adolescents participating in the Fast Track study reported valuing dietetic support early in the interventions and felt the final phase when dietetic support was reduced was the most difficult to “stay on track” [38]. The value of a supportive therapeutic relationship has been previously documented [39] and may in part explain the transient improvements in some measures of eating behaviors and psychosocial health. Indeed, receiving compassion from others and self-compassion is associated with body appreciation, which may in turn influence eating behaviors [33].

The strength of this study is that we address an important clinical research gap by reporting psychosocial health outcomes following an intensive dietary intervention, with longitudinal data up to 12 months. We have previously reported the intensive behavioral interventions, implemented by an experienced multidisciplinary team, improved BMI, blood pressure percentile, total cholesterol, triglycerides, and symptoms of depression and eating disorders. We also had some limitations. First, we were not powered to detect clinical or statistically significant findings in psychosocial outcomes. The sample size calculations were based on changes in primary outcome, BMIz, and minimally important differences relevant for clinical interpterion of change in the range of psychosocial outcomes are not defined [40, 41]. Second, as previously reported, two participants were withdrawn from the study by investigators due to mental health concerns. Finally, it is possible that poorer psychological health outcomes may not be captured using current assessment tools [40–42], and robust evaluation and reporting of psychosocial health within obesity treatment is an important area for further research [41, 43].

Conclusion

This intensive behavioral program improved some psychosocial outcomes for adolescents with obesity-associated complications. The improvements in psychosocial health were not different between dietary interventions and may be due to engagement with a health professional-led behavioral intervention. Longer term follow-up is needed to determine whether improvements are sustained following removal of health professional support or transition to primary care with reduced support.

Acknowledgments

Fast Track to Health Study Team were as follows: Shirley Alexander, MBChB, MPH; Louise A Baur, MBBS, PhD; Justin Brown, MB, BChir, MA, DipClinSci; Clare E Collins, PhD; Christopher T Cowell, MBBS; Kaitlin Day, PhD; Sarah P Garnett, PhD; Megan L Gow, PhD; Alicia M Grunseit, BNutrDiet; Eve T House, MNutriDiet; Mary-Kate Inkster, BNutriDiet; Hiba Jebeile, PhD; Cathy Kwok, MClinPsych; Sarah Lang, PhD; Natalie B Lister, PhD; Susan J Paxton, PhD; Helen Truby, PhD; and Krista A Varady PhD. Additional contributions were as follows: Katharine Aldwell, MNutrDiet; Kim L. Alman, BSci, MNutrDiet; Maddison Henderson, MNutrDiet; Andriana Korai, MNutrDiet; Alan J. McCubbin, PhD; Gerri A. Minshall, MPsych (Clinical); Kerryn Roem, Grad Dip Dietetics; and Sarah Thomas, BNutrDiet (Class 1 Hons), contributed to clinical care and data collection, while they were employed at The Children’s Hospital at Westmead, Westmead, NSW, Australia, and Monash Children’s Hospital, Clayton, VIC, Australia. They received no additional compensation outside their salaries. We thank the adolescents and their families for participating in this research.

Statement of Ethics

This study protocol was reviewed and approved by The Sydney Children’s Hospitals Network Human Research Ethics Committee, Approval No. HREC/17/SCHN/164. Written informed consent from parents and agreement from adolescents was obtained prior to their enrollment in the study.

Conflict of Interest Statement

Dr Baur reported receiving speakers’ fees from Novo Nordisk with funds directed to the hospital cost center and serving as a member of the Eli Lilly Advisory Committee outside the submitted work. Ms Kwok reported receiving travel support from Novo Nordisk to attend and present the ACTION Teens study (a survey study funded by Novo Nordisk) at the Australian and New Zealand Obesity Society (ANZOS) Annual Scientific Meeting 2023 in Adelaide, Australia, outside the submitted work. Dr Varady reported receiving author fees from Pan MacMillan Publishing for the book The Fastest Diet outside the submitted work. No other disclosures were reported.

Funding Sources

This study was funded by grant 1128317 from the National Health and Medical Research Council of Australia (NHRMC). Dr Lister is supported by grant 114574 from the NHMRC Peter Doherty Early Career Fellowship program. Dr Baur is supported by an NHMRC Leadership (L3) Investigator Grant 2009035. Dr Gow is supported by NHMRC Peter Doherty Early Career Fellowship 1158876. Ms Kwok is supported by a University of Sydney Postgraduate Awards scholarship. Dr Varady is supported by grants R01DK128180, R01CA257807, and R01DK119783 from the National Institutes of Health. Dr Jebeile is supported by an NHMRC Emerging Leadership Investigator Grant 2017139. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Author Contributions

N.B.L. conceptualized and designed the study, obtained funding, supervised the data collection, conducted statistical analysis, drafted the manuscript, and revised the manuscript for important intellectual content. L.A.B. conceptualized and designed the study, obtained funding, delivered the interventions, supervised the data collection, and revised the manuscript for important intellectual content. M.L.G. conceptualized and designed the study, obtained funding, supervised the data collection, and revised the manuscript for important intellectual content. E.T.H. delivered the interventions, collected data, supervised the data collection, and revised the manuscript for important intellectual content. C.K. delivered the interventions, collected data, supervised the data collection, and revised the manuscript for important intellectual content. K.A.V. conceptualized and designed the study, obtained funding, and revised the manuscript for important intellectual content. H.J. conceptualized and designed the study, supervised the data collection, and revised the manuscript for important intellectual content.

Funding Statement

This study was funded by grant 1128317 from the National Health and Medical Research Council of Australia (NHRMC). Dr Lister is supported by grant 114574 from the NHMRC Peter Doherty Early Career Fellowship program. Dr Baur is supported by an NHMRC Leadership (L3) Investigator Grant 2009035. Dr Gow is supported by NHMRC Peter Doherty Early Career Fellowship 1158876. Ms Kwok is supported by a University of Sydney Postgraduate Awards scholarship. Dr Varady is supported by grants R01DK128180, R01CA257807, and R01DK119783 from the National Institutes of Health. Dr Jebeile is supported by an NHMRC Emerging Leadership Investigator Grant 2017139. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Data Availability Statement

The data that support the findings of this study are not publicly available due to ethical requirements. Data may be shared subject to further ethics approval. Further inquiries can be directed to the corresponding author.