Imagine HEALTH: Randomized Controlled Trial of a Guided Imagery Lifestyle Intervention to Improve Obesity-Related Lifestyle Behaviors in Predominantly Latinx Adolescents

Abstract

Introduction:

To determine the effects of a novel lifestyle intervention combining lifestyle behavioral education with the complementary–integrative health modality of guided imagery (GI) on dietary and physical activity behaviors in adolescents. The primary aim of this study was to determine the incremental effects of the lifestyle education, stress reduction GI (SRGI), and lifestyle behavior GI (LBGI) components of the intervention on the primary outcome of physical activity lifestyle behaviors (sedentary behavior, light, moderate, and vigorous physical activity), as well as dietary intake behaviors, at the completion of the 12-week intervention. The authors hypothesized that the intervention would improve obesity-related lifestyle behaviors.

Materials and Methods:

Two hundred and thirty-two adolescent participants (aged 14–17 years, sophomore or junior year of high school) were cluster randomized by school into one of four intervention arms: nonintervention Control (C), Lifestyle education (LS), SRGI, and LBGI. After-school intervention sessions were held two (LS) or three (SRGI, LBGI) times weekly for 12 weeks. Physical activity (accelerometry) and dietary intake (multiple diet recalls) outcomes were assessed pre- and postintervention. Primary analysis: intention-to-treat (ITT) mixed-effects modeling with diagonal covariance matrices; secondary analysis: ad hoc subgroup sensitivity analysis using only those participants adherent to protocol.

Results:

ITT analysis showed that the Healthy Eating Index (HEI) increased in the LS group compared with C (p = 0.02), but there was no additional effect of GI. Among adherent participants, sedentary behavior was decreased stepwise relative to C in SRGI (d = −0.73, p = 0.004) > LBGI (d = −0.59, p = 0.04) > LS (d = −0.41, p = 0.07), and moderate + vigorous physical activity was increased in SRGI (d = 0.58, p = 0.001). Among adherent participants, the HEI was increased in LS and SRGI, and glycemic index reduced in LBGI.

Conclusions:

While ITT analysis was negative, among adherent participants, the Imagine HEALTH lifestyle intervention improved eating habits, reduced sedentary activity, and increased physical activity, suggesting that GI may amplify the role of lifestyle education alone for some key outcomes. Clinical Trials.gov ID: NCT02088294

Introduction

Latinx adolescents suffer from a high prevalence of obesity¹ and obesity-related comorbidities, such as type 2 diabetes.^2
–4 Insulin resistance, rather than body fat per se, is the primary pathophysiological factor leading to metabolic disease risk.^5,6 Therefore, targeting reductions in insulin resistance through changing modifiable lifestyle behaviors, such as eating and physical activity, is key in the prevention of type 2 diabetes in overweight adolescents.^7

–10

While chronic stress has been linked both to the development of obesity and obesity-related morbidities, previous intervention strategies have not addressed this issue nor have they utilized complementary mind–body modalities to reduce chronic stress as part of an integrative approach to obesity prevention and/or treatment. The authors' previously reported pilot intervention for Latinx adolescents with obesity¹¹ showed that compared with lifestyle education controls, individual Interactive Guided Imagery^SM added to lifestyle education acutely reduced the stress biomarker salivary cortisol, reduced sedentary behavior, and increased moderate physical activity compared with lifestyle education alone.¹¹

The authors now describe the primary outcomes of a randomized controlled trial (RCT) in predominantly Latinx adolescents of a novel lifestyle intervention that uses lifestyle behavioral education combined with guided imagery (GI) designed to reduce stress and improve lifestyle behaviors. The primary aim of this study was to determine the incremental effects of the didactic lifestyle education (LS), stress reduction GI (SRGI), and lifestyle behavior GI (LBGI) components of the intervention on physical activity behaviors (including sedentary behavior, light, moderate, and vigorous physical activity) at the completion of the 12-week intervention. The changes in dietary behavior following intervention were also assessed. The authors hypothesized that all intervention arms would show improvement in obesity-related lifestyle behaviors beyond nonintervention control and that SRGI and LBGI arms of the intervention would show greater improvement in these outcomes than LS alone, with the greatest improvement expected in LBGI.

Materials and Methods

Study design

The full Imagine HEALTH protocol has been previously described in detail.¹² High school sophomores and juniors, aged 14–17 years, were recruited during in-person study team visits to required classes (History and English) in four urban high schools, prescreened, and subsequently called by study staff for full eligibility screening. Two hundred and thirty-two eligible participants underwent group consenting and enrollment visits (Fig. 1).¹² Reasons for exclusion (some participants had multiple reasons) included: inadequate time available (n = 750); incorrect age or grade (n = 19); serious chronic illness or medications (n = 27); eating disorder, psychiatric disorder, cognitive or behavioral disability (n = 29); lack of English fluency (n = 8); prior participation in school council programs (n = 5); sibling in the program (n = 3); concurrent after-school activities that interfere with intervention attendance (n = 214).

FIG. 1.

Consort diagram. GI, guided imagery; LBGI, lifestyle behavior GI; LS, lifestyle education; SRGI, stress reduction GI.

The intervention was conducted in three successive annual waves from January to May, 2015–2017, ending as planned at completion of the intervention. Cluster randomization was performed at the school level. Before each wave, one of the four study arms was randomly assigned to each school. Blocking was implemented such that no school could get the same study arm more than once across the three waves of the study. Across the total duration of the study, each school delivered three of the four different arms of the intervention.

The four intervention arms were: (1) nonintervention “Control” (C); (2) “Lifestyle education” (LS), consisting of 12 weeks of twice weekly 75-min sessions of didactic and experiential education relating to healthy eating (one session per week) and physical activity (one session per week) practices consistent with consensus pediatric recommendations,^12

–15 in particular emphasizing modification in quality of carbohydrate intake^8,16,17 and key concepts of “Intuitive Eating,”^18
–20 a nondieting approach to healthy eating; (3) “SRGI”, which received the same lifestyle education plus an additional once weekly 75-min group SRGI session for 10 sessions; (4) “LBGI”, which received the same lifestyle education, plus four weekly 75-min group SRGI sessions, followed by six weekly sessions of GI designed to motivate improved eating and activity behaviors. The final two weekly sessions for both the SRGI and LBGI arms contained imagery content that integrated the entire 12-week program. Group GI was delivered in the context of the facilitated group process known as “council,” with specific imagery content as previously detailed.^12,21

This study was approved by the Internal Review Board (IRB, #HS-13-00836) of the University of Southern California Health Science Campus. Parents signed informed consent, and participants signed youth assent forms. This trial was registered with Clinical Trials.gov (https://clinicaltrials.gov). Consort checklist can be found in Supplementary Data.

Outcome measures

Outcome measures were assessed at baseline (preintervention) and upon completing the 12-week intervention (postintervention).¹²

Physical activity (primary outcome)

Study participants wore the triaxial Actigraph accelerometer model GT3X+ on their nondominant wrist for 1-week measurement period,¹² set to collect movement information at the frequency of 60 Hz. Wear time validation was conducted using the criteria defined by Choi et al.²² and was cross-checked with self-reported nonwear time documented in a paper log. Only participants with at least four valid wear days, defined as 10 or more hours of valid wear time, were included in the data set (5 excluded at baseline, 11 excluded at 3 months). Total minutes spent in sedentary behavior (vector magnitude [VM per 5 sec] <305), light (VM 306–817), moderate (VM 818–1,968), and vigorous (VM >1,968) intensity activities were defined in accordance with thresholds described in Chandler et al.²³

Dietary intake

Dietary intake was collected¹² using multiple pass dietary recall interviews using the Nutrition Data System for Research (NDS-R version 2014–2017), a well-validated 24-hour recall dietary assessment method.^24,25 Main dietary outcome variables for this report included total daily energy (calories), macronutrients, total and added sugars, fiber (soluble and insoluble), glycemic load and glycemic index, and the Healthy Eating Index (HEI)-2015, a validated, composite eating index composed of 13 components that reflect the different food groups and key recommendations in the 2015–2020 Dietary Guidelines for Americans. ^26,27 The mean energy intake was regressed on body mass index (BMI), and recalls from nine participants (seven from baseline and two from post-test) for which the resulting standard residual was >2 were considered implausible and excluded from analysis.

Program adherence

Attendance to intervention sessions was defined as being present for at least 45 min of the 75-min class, inclusive of participation in the GI exercise. Adherence was defined on the individual participant level as attendance by the participant to at least 75% of lifestyle classes and 75% of GI sessions. For the purposes of the intention-to-treat (ITT) analysis, the authors defined adherence a priori at the group level as 80% of participants attending at least 75% of classes. Adherence was monitored throughout the conduct of the intervention, and measures for improving adherence implemented when needed. These included utilizing young adult study staff to build rapport with participants, making multiple text/phone call reminders of class sessions, mailing of holiday/birthday cards, and offering a variety of cash and noncash (gift cards, movie tickets) incentives, scholastic service learning credits, and letters of recognition for personal portfolio use.¹²

Adverse events

Adverse events and serious adverse events were assigned using standard clinical research definitions and were defined as definitely unrelated, definitely related, probably related, or possibly related to study procedures.¹² All adverse events were tracked, documented, and reported to the Independent Monitoring Committee annually.

Secondary study outcomes assessed

Changes in subjective stress, cortisol biomarkers, anthropometrics, and diabetes-related biomarkers were measured and will be addressed in subsequent reports.

Statistical analyses

Statistical analyses were conducted according to the methodology detailed in the study protocol,¹² Briefly, the ITT population includes all participants randomized within the schools. Results display differences in sample size from one measurement to the next, as not every student completed every measurement at baseline or 3 months. All analyses were nested within schools to account for the variability shared within school environment. Statistical modeling of continuous outcomes was accomplished through the use of mixed-effects modeling with diagonal covariance matrices, whereas categorical outcomes were compared using generalized estimating equations. Preliminary analyses of preintervention values of outcomes and participant characteristics were compared across groups to assure that randomization was successful across intervention groups. Participant characteristics that were unequal at baseline (evaluated using analysis of variance F, Fisher's exact, or chi-squared tests) were also included as covariates in analyses. Group effects were assessed using omnibus hypotheses across all groups with the primary endpoint of 12 weeks, followed by post hoc comparisons of group effect. A priori covariates included baseline values, sex, ethnicity, race, BMI (dichotomous indicator of normal vs. overweight at baseline), and year in the study. To evaluate possible group effect differences by BMI categories, the interaction term of treatment group by BMI was added in the model, but dropped due to insignificant association with outcomes.

Additional ad hoc analyses were performed. Change dichotomized into positive or negative was performed for the outcomes, in which comparisons were made using c² tests to examine the prevalence of improvement across groups. Subgroup sensitivity analysis using only those participants adherent to protocol was performed with ITT model, adjusting for school clustering. A priori power was limited to the primary analyses; thus, for pairwise comparisons, the authors present Cohen's d effect sizes to assess the clinical impact of the difference in intervention. The authors also report p-values, so that the reader can apply a post hoc alpha adjustment of their choice.

Results

Demographics and adherence

Figure 1 shows the flow of participants through recruitment, consenting, randomization, intervention delivery, and outcome measurement. Of 232 enrolled participants, 184 (79%) completed at least one primary outcomes measurement visit at the completion of the 12-week intervention (3-month follow-up).

Table 1 shows baseline demographic and clinical characteristics for the four intervention groups. Overall, 64% of participants were in the 11th grade, 66% were female, 94% were Latinx, and 40% had obesity/overweight. There were no baseline differences in weight, BMI, or other physical health variables between the groups. There were significant baseline differences between the groups in age, grade, and race, and these were thus used as covariates in subsequent analytical models.

Table 1.

Participant Baseline Demographics and Clinical Characteristics by Treatment Group

	Control (n = 51) n (%)	LS (n = 61) n (%)	LBGI (n = 55) n (%)	SRGI (n = 65) n (%)	Total (n = 232) n (%)	p-Value
Grade
10th	11 (22)	31 (51)	23 (42)	19 (29)	84 (36)	0.01
11th	40 (78)	30 (49)	32 (58)	46 (71)	148 (64)
Sex
Female	38 (75)	36 (59)	40 (73)	40 (62)	154 (66)	0.20
Male	13 (25)	25 (41)	15 (27)	25 (38)	78 (34)
Ethnicity
Hispanic or Latino	50 (98)	56 (92)	51 (93)	61 (94)	218 (94)	0.76
Not Hispanic or Latino	1 (2)	4 (7)	3 (5)	4 (6)	12 (5)
Not reported	0 (0)	1 (2)	1 (2)	0 (0)	2 (1)
Race
American Indian/Alaska Native	0 (0)	0 (0)	1 (2)	0 (0)	1 (0)	0.02
Asian	1 (2)	5 (8)	1 (2)	1 (2)	8 (3)
Black or African American	0 (0)	0 (0)	0 (0)	2 (3)	2 (1)
White	50 (98)	55 (90)	46 (84)	57 (88)	208 (90)
Other/more than one race	0 (0)	1 (2)	3 (5)	1 (2)	5 (2)
Not reported	0 (0)	0 (0)	4 (7)	4 (6)	8 (3)
BMI category
Underweight (<5th percentile)	2 (4)	2 (3)	2 (4)	1 (2)	7 (3)	0.41
Normal (5–84th percentile)	28 (55)	32 (52)	32 (58)	25 (38)	117 (50)
Overweight (85–94th percentile)	8 (16)	7 (11)	9 (16)	17 (26)	41 (18)
Obese (95th+ percentile)	11 (22)	13 (21)	8 (15)	18 (28)	50 (22)

	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	p-Value
Age (years)	16.5 ± 0.5	16.2 ± 0.7	16.3 ± 0.6	16.6 ± 0.6	16.4 ± 0.6	0.01
Systolic blood pressure (mmHg)	107 ± 25	108 ± 28	106 ± 27	111 ± 24	108 ± 26	0.70
Diastolic blood pressure (mmHg)	66 ± 15	64 ± 17	66 ± 17	67 ± 15	66 ± 16	0.81
Height (cm)	155 ± 33	158 ± 31	152 ± 38	157 ± 30	156 ± 33	0.75
Weight (kg)	66 ± 22	66 ± 18	61 ± 16	68 ± 17	65 ± 18	0.19
Waist circumference (cm)	83 ± 23	80 ± 23	77 ± 23	85 ± 20	82 ± 22	0.27
BMI (kg/m²)	24.9 ± 6.4	24.3 ± 6	23.4 ± 5.1	25.7 ± 5.4	24.6 ± 5.7	0.17
BMI z-score	0.7 ± 1.2	0.6 ± 1.2	0.4 ± 1.1	0.9 ± 1.2	0.6 ± 1.2	0.21

BMI, body mass index.

The average adherence of all intervention groups was 41% (i.e., 41% of participants attended at least 75% of all possible intervention sessions, compared with the a priori adherence target of 80%). The LS group (twice weekly sessions) had 52% adherence, whereas SRGI and LBGI (thrice weekly sessions) had 37% and 33% adherence, respectively (p = 0.04, by chi-squared). For LS, LBGI, and SRGI groups, adherence to nutrition classes was 61%, 42% and 40%, and for physical activity classes was 39%, 27%, and 22%, respectively. Adherence for GI sessions was 45% in LBGI and 38% in SRGI. Despite overall lower adherence in the GI groups, the total number of actual after-school sessions attended per participant in the three intervention groups was not significantly different (13.3 ± 7.6 of 24 total for LS, 16.7 ± 11.9 of 36 total for SRGI, and 17.6 ± 11.3 of 36 total for LBGI). Attendance was higher in the first 6 weeks of the intervention (59% average session attendance for all three groups combined), compared with weeks 7–12 (47% average session attendance).

Lifestyle behaviors: ITT analysis

Table 2 shows the ITT analysis of changes in dietary intake and physical activity outcomes from baseline to postintervention. There were no between-group differences in sedentary behavior or physical activity. A significant increase was seen in the HEI for the LS group compared with nonintervention C (p = 0.02), along with a trend toward an increase in HEI for LBGI versus C (p = 0.08). The LBGI group additionally showed a marginally significant increase in insoluble fiber (p = 0.06). There were no between-group differences in other dietary intake outcomes. There were no differences in any of the ITT outcomes in participants who had overweight/obesity compared with those participants who were normal weight. In the additional post hoc analysis, the percentage of subjects who showed any degree of decrease in sedentary behavior postintervention compared with baseline was 33%, 62%, 29%, and 54% in C, LS, LBGI, and SRGI groups, respectively, with LS and SRGI showing more participants who decreased sedentary behavior than would be expected (p = 0.035). This analysis showed no other significant changes in the other physical activity behaviors or dietary intake outcomes.

Table 2.

Intention-to-Treat Analysis of Dietary Intake and Physical Activity Outcomes

	Group	Baseline Mean ± SD	3 Months Mean ± SD	n	Change ^a Mean ± SD	Estimated marginal Mean (95% CI)^b	p-Value
Dietary intake
Energy (kCal/day)	Control	1,551.8 ± 617.7	1,671.6 ± 1,480.3	30	125.3 ± 1,338.9	310.3 (−64 to 684.7)
	LS	1,621 ± 688.2	1,652.6 ± 640.7	33	−45.5 ± 624.9	173.1 (−198.3 to 544.6)	0.58
	LBGI	1,726.6 ± 1,075.3	1,672.9 ± 697	22	−86.8 ± 787.8	284.7 (−161.8 to 731.2)	0.92
	SRGI	1,553.1 ± 634.5	1,527.2 ± 597.7	27	−121.1 ± 697.9	47.3 (−334.3 to 429)	0.28
Carbohydrate (g/day)	Control	200.6 ± 68.8	213.9 ± 148.8	30	12.8 ± 123.5	37.5 (−4.5 to 79.5)
	LS	196.7 ± 76.1	207.3 ± 72.8	33	−2.2 ± 72.7	20.9 (−20.4 to 62.1)	0.53
	LBGI	220.7 ± 126.5	210.4 ± 93.1	22	−21 ± 108.4	22.8 (−26.4 to 72)	0.61
	SRGI	194 ± 80	192.3 ± 84.6	27	−9.1 ± 95.4	11.9 (−31.3 to 55)	0.33
Total sugar (g/day)	Control	84.1 ± 35.1	86.1 ± 44.6	30	0.5 ± 49.3	6 (−13.8 to 25.8)
	LS	84.2 ± 41.9	87.2 ± 37.2	33	−1.9 ± 41	1.7 (−17.9 to 21.3)	0.74
	LBGI	88.3 ± 44	95.2 ± 62.6	22	−4.3 ± 69.1	8.8 (−14.9 to 32.5)	0.85
	SRGI	85.8 ± 49.1	85.5 ± 50.5	27	−7.3 ± 60.7	2.1 (−18 to 22.2)	0.76
Added sugar (g/day)	Control	47.6 ± 28.7	49.8 ± 36	30	2 ± 42.5	8.6 (−6 to 23.3)
	LS	44.8 ± 29.2	40.8 ± 29.6	33	−5.3 ± 26.8	−1.5 (−16 to 13)	0.30
	LBGI	47.4 ± 38.4	47.7 ± 37.9	22	−3.7 ± 57.4	0.8 (−16.7 to 18.3)	0.46
	SRGI	47.6 ± 35	43.2 ± 42.5	27	−4.1 ± 42.4	2.9 (−12 to 17.8)	0.55
Soluble fiber (g/day)	Control	4.9 ± 2.4	4.5 ± 3.8	30	−0.5 ± 4	0.8 (−0.6 to 2.3)
	LS	4.6 ± 2.6	4.8 ± 2.7	33	−0.3 ± 2.8	0.4 (−1.1 to 1.9)	0.66
	LBGI	4.8 ± 3	4.8 ± 2.4	22	−0.1 ± 2.5	1.5 (−0.2 to 3.2)	0.53
	SRGI	4.3 ± 2.6	5.3 ± 5.2	27	0.5 ± 6.1	1.2 (−0.3 to 2.7)	0.74
Insoluble fiber (g/day)	Control	9.4 ± 5.3	8.6 ± 5.3	30	−1.2 ± 5.9	−0.3 (−2.4 to 1.7)
	LS	10.4 ± 6.5	10.8 ± 5.8	33	−0.5 ± 4.7	0.3 (−1.7 to 2.4)	0.63
	LBGI	9.6 ± 5.7	11.4 ± 6.2	22	1.2 ± 5.8	2.4 (0 to 4.9)	0.06
	SRGI	8.7 ± 4.5	10.3 ± 6.4	27	0.8 ± 5.6	0.7 (−1.4 to 2.8)	0.45
Total fiber (g/day)	Control	14.3 ± 7.4	13.2 ± 8.8	30	−1.7 ± 9.2	0.1 (−4.4 to 4.5)
	LS	15.1 ± 8.9	15.7 ± 8.4	33	−0.9 ± 7.1	0.4 (−3.4 to 4.3)	0.86
	LBGI	14.5 ± 8.6	16.2 ± 8.4	22	1 ± 7.8	3.4 (−0.9 to 7.7)	0.14
	SRGI	13 ± 6.6	15.8 ± 9.8	27	1.3 ± 9.8	1.5 (−2.6 to 5.6)	0.49
Total protein (g/day)	Control	64.5 ± 34.5	65.7 ± 61.6	31	−1.3 ± 65.2	1.1 (−22.2 to 24.4)
	LS	68.1 ± 35.1	73.7 ± 31.8	35	4.5 ± 31.6	5.9 (−13.8 to 25.6)	0.64
	LBGI	65.2 ± 33.1	66.3 ± 28.4	24	−3.9 ± 25.5	4.3 (−17.9 to 26.6)	0.78
	SRGI	64.7 ± 28.6	70.3 ± 25.1	31	−5.5 ± 35.7	−3.8 (−24.9 to 17.4)	0.63
Total fat (g/day)	Control	56.7 ± 31.3	62.6 ± 70.5	31	7.3 ± 67.1	10.3 (−15.3 to 35.9)
	LS	64.4 ± 37.7	62.1 ± 30.5	35	−7.1 ± 34.6	3.1 (−18.8 to 25)	0.53
	LBGI	64.2 ± 54.7	65.3 ± 37	24	2.3 ± 43.9	13.9 (−10.5 to 38.3)	0.78
	SRGI	58.7 ± 32.3	55.9 ± 26.1	31	−10.2 ± 33.6	−4.6 (−28 to 18.7)	0.19
Healthy Eating Index	Control	50.9 ± 11.3	49.7 ± 10.2	31	−2 ± 9.8	−3.2 (−7.3 to 1)
	LS	52 ± 10.1	54.7 ± 10.5	34	3.5 ± 11.6	3.5 (−0.6 to 7.6)	0.02
	LBGI	49.9 ± 11.4	53.4 ± 10.2	23	2.5 ± 13.8	2 (−2.9 to 6.9)	0.08
	SRGI	52.5 ± 10.5	53.4 ± 12	31	−0.7 ± 13.8	0.3 (−3.8 to 4.4)	0.19
Glycemic load	Control	111.2 ± 41.9	120 ± 94.1	30	9.1 ± 77.6	25.9 (1.4 to 50.3)
	LS	107.3 ± 43.1	111.3 ± 40.5	33	−1.9 ± 42.1	12 (−12.1 to 36.2)	0.39
	LBGI	123.9 ± 77.3	111 ± 49.9	22	−17 ± 66.1	9 (−20.2 to 38.1)	0.33
	SRGI	107.1 ± 43.5	100.6 ± 47.3	27	−8.6 ± 53.1	5.6 (−19.5 to 30.6)	0.20
Glycemic index	Control	59.3 ± 4.1	58.5 ± 5	30	−0.7 ± 6	0.6 (−1.4 to 2.6)
	LS	58.9 ± 4.8	57.9 ± 4.5	33	−0.2 ± 6.1	0 (−2 to 2)	0.63
	LBGI	58.9 ± 4.8	57.2 ± 4.8	22	−0.6 ± 6.4	−1 (−3.4 to 1.4)	0.26
	SRGI	59.3 ± 4.3	57.1 ± 5.4	27	−1.4 ± 5.9	−0.3 (−2.4 to 1.7)	0.48
Physical activity^c
Sedentary behavior (min/day)	Control	1,085.5 ± 106	1,099.4 ± 122.4	40	18.7 ± 102	31.5 (−17 to 80)
	LS	1,079.2 ± 100.2	1,084.1 ± 136.9	41	−0.1 ± 101.2	13 (−35.5 to 61.4)	0.54
	LBGI	1,053.3 ± 75	1,052.1 ± 204.6	34	7.4 ± 204.9	−3.1 (−56.4 to 50.2)	0.28
	SRGI	1,084 ± 114.2	1,061.8 ± 150.1	34	0.6 ± 129.8	3.5 (−45.9 to 52.9)	0.37
Light activity (min/day)	Control	21.6 ± 8.7	21.4 ± 12.3	40	−1.2 ± 12.1	0.6 (−5.1 to 6.3)
	LS	22.2 ± 7.6	21.8 ± 12.6	41	−0.2 ± 12.2	1.6 (−3.6 to 6.7)	0.71
	LBGI	24.4 ± 8.2	23.5 ± 13.1	34	−1.8 ± 9.9	1.4 (−4.1 to 6.8)	0.78
	SRGI	21.2 ± 6.9	24.1 ± 14.5	34	1.4 ± 15.1	2.7 (−2.7 to 8.2)	0.42
Moderate activity (min/day)	Control	52.4 ± 17.8	48 ± 20.7	40	−6.6 ± 18.8	−3.8 (−13.4 to 5.7)
	LS	52.9 ± 13.4	50 ± 22.9	41	−3.1 ± 18.2	−0.2 (−8.9 to 8.5)	0.40
	LBGI	59.1 ± 14.8	53.1 ± 23.2	34	−7.7 ± 17.9	−2.6 (−11.8 to 6.6)	0.79
	SRGI	52 ± 17.6	53.5 ± 25.2	34	−2.4 ± 24.3	0.3 (−8.9 to 9.4)	0.36
Vigorous activity (min/day)	Control	255.1 ± 86	225.6 ± 90.2	40	−36.7 ± 63.8	−29.5 (−68.1 to 9.1)
	LS	257.4 ± 73.4	239.3 ± 95.6	41	−21.2 ± 65.9	−12.8 (−48 to 22.4)	0.35
	LBGI	284.9 ± 54.8	243 ± 92.4	34	−48.3 ± 86.5	−29.5 (−66.9 to 7.9)	0.99
	SRGI	261.3 ± 87	252.5 ± 107.2	34	−29.8 ± 95.6	−19.8 (−56.8 to 17.3)	0.59
Moderate + vigorous activity (min/day)	Control	307.5 ± 102.1	273.6 ± 108.4	40	−43.3 ± 81.4	−33.1 (−80.5 to 14.4)
Moderate + vigorous activity (min/day)	LS	310.3 ± 84.9	289.4 ± 117.2	41	−24.3 ± 82.2	−12.7 (−56 to 30.7)	0.35
	LBGI	344 ± 65.6	296 ± 112.8	34	−56 ± 103.5	−32.3 (−78.4 to 13.8)	0.97
	SRGI	313.3 ± 103.5	306 ± 130.6	34	−32.2 ± 118.5	−19.2 (−64.7 to 26.4)	0.53

Difference score among participants with data for baseline and 3-month assessment. Participants' missing data for baseline and/or 3-month assessments are not included in the table.

Estimated marginal mean for change (difference score). Analyses nested in school. Adjusted for a priori covariates (baseline measurement, sex, Hispanic ethnicity, BMI, and year in study) and baseline characteristics, which were unbalanced between treatment groups (grade, age, and race).

Mean number of minutes per day across 7-day observation period.

BMI, body mass index; GI, guided imagery; LBGI, lifestyle behavior GI; LS, lifestyle education; SRGI, stress reduction GI.

Lifestyle behaviors: sensitivity analysis (adherent participants only)

Table 3 shows the post hoc sensitivity analysis of changes in dietary intake and physical activity outcomes from baseline to postintervention, performed only on those participants who achieved the adherence goal of attending 75% of all intervention sessions. Stepwise larger reductions in sedentary behavior were observed in LS (d = −0.41, p = 0.07), LBGI (d = −0.59, p = 0.04), and SRGI (d = −0.73, p = 0.004) compared with C (Fig. 2). Combined moderate + vigorous physical activity (MVPA) increased in the SRGI group (d = 0.58, p = 0.001 vs. C) and was also higher in LS (d = 0.36, p < 0.05) compared with C. Light physical activity was higher in SRGI versus C (d = 0.38, p = 0.03). The HEI improved in the LS and SRGI groups, with a moderate effect size compared with C. The glycemic index was significantly reduced in the LBGI group, with a large effect size (d = −0.84, p = 0.01), and showed a moderate effect size reduction in SRGI, although nonsignificant (d = −0.48, p = 0.12). There were no significant effects observed in the other dietary variables assessed.

FIG. 2.

Changes in sedentary behavior and physical activity. Bars depict mean ± 95% confidence interval. p-Value versus Control: *p < 0.05; **p < 0.01. GI, guided imagery; LBGI, lifestyle behavior GI; LS, lifestyle education; SRGI, stress reduction GI.

Table 3.

Sensitivity Analysis of Dietary Intake and Physical Activity Outcomes

	Group	Baseline Mean ± SD	3 Months Mean ± SD	n	Change ^a Mean ± SD	Estimated marginal Mean (95% CI)^b	p-Value	Cohen's d
Dietary intake
Energy (kCal/day)	Control	1,551.8 ± 617.7	1,671.6 ± 1,480.3	30	125.3 ± 1,338.9	49.1 (−344.5 to 442.8)
	LS	1,701.2 ± 778.5	1,732.8 ± 593.5	26	−43.5 ± 626	26 (−399.1 to 451.2)	0.93	−0.02
	LBGI	1,718.6 ± 638.8	1,836.2 ± 780.4	13	−69.8 ± 842.3	25.5 (−543.5 to 594.4)	0.94	−0.02
	SRGI	1,541.1 ± 692	1,502.9 ± 636.6	17	−155.3 ± 741.2	−202.5 (−701.5 to 296.5)	0.39	−0.24
Carbohydrate (g/day)	Control	200.6 ± 68.8	214 ± 148.8	30	12.8 ± 123.5	7.5 (−30.9 to 45.9)
	LS	207.9 ± 81.6	216.9 ± 62.6	26	−2.3 ± 68.6	1 (−40.4 to 42.4)	0.81	−0.06
	LBGI	225.1 ± 100.8	228.9 ± 100.6	13	−21.8 ± 110.5	−10.1 (−67.4 to 47.3)	0.61	−0.17
	SRGI	189.7 ± 87.6	195.4 ± 91.2	17	−7.8 ± 96	−12.4 (−62.2 to 37.4)	0.51	−0.19
Total sugar (g/day)	Control	84.1 ± 35.1	86.1 ± 44.6	30	0.5 ± 49.3	−4.3 (−21.6 to 12.9)
	LS	89.9 ± 41.8	93.7 ± 37.3	26	−1.7 ± 41.5	0 (−18.4 to 18.5)	0.73	0.09
	LBGI	92.9 ± 46.4	113.9 ± 71.6	13	9.2 ± 76.4	16.8 (−9.4 to 43)	0.19	0.44
	SRGI	85.2 ± 52.6	87.6 ± 54.8	17	−5.3 ± 59.1	−5.2 (−27.9 to 17.6)	0.95	−0.02
Added sugar (g/day)	Control	47.7 ± 28.7	49.8 ± 36	30	2 ± 42.5	0.4 (−12.8 to 13.7)
	LS	47 ± 29.8	42.6 ± 30.5	26	−7.5 ± 29.3	−7.4 (−21.6 to 6.8)	0.42	−0.22
	LBGI	45.6 ± 46.4	50.1 ± 45.3	13	−6.2 ± 69.7	−1.4 (−21.6 to 18.8)	0.88	−0.05
	SRGI	42.4 ± 34.2	43.2 ± 42.5	17	−5.3 ± 43.7	−6.4 (−24 to 11.3)	0.54	−0.19
Soluble fiber (g/day)	Control	4.9 ± 2.4	4.5 ± 3.8	30	−0.5 ± 4	−0.4 (−1.9 to 1)
	LS	4.7 ± 2.8	5 ± 2.4	26	0 ± 2.8	0 (−1.5 to 1.6)	0.65	0.12
	LBGI	5.3 ± 2.4	5.5 ± 2.8	13	0.2 ± 2.9	0.4 (−1.8 to 2.6)	0.53	0.21
	SRGI	3.9 ± 2.7	6.3 ± 6.4	17	1.9 ± 7.1	1.5 (−0.5 to 3.4)	0.12	0.48
Insoluble fiber (g/day)	Control	9.4 ± 5.3	8.6 ± 5.4	30	−1.2 ± 5.9	−1.6 (−3.3 to 0.2)
	LS	11 ± 6.7	11.5 ± 4.8	26	−0.3 ± 4.9	0.3 (−1.6 to 2.1)	0.16	0.38
	LBGI	11 ± 4.8	12.5 ± 6.7	13	1.2 ± 6.7	1.5 (−1.1 to 4.1)	0.06	0.64
	SRGI	8.6 ± 5.7	10.7 ± 6.1	17	1.1 ± 4.7	0.6 (−1.7 to 2.9)	0.13	0.46
Total fiber (g/day)	Control	14.3 ± 7.4	13.2 ± 8.8	30	−1.7 ± 9.2	−2.1 (−5 to 0.8)
	LS	15.8 ± 9.4	16.6 ± 7	26	−0.5 ± 7.3	0.2 (−2.9 to 3.3)	0.29	0.28
	LBGI	16.4 ± 6.8	18 ± 9.3	13	1.2 ± 9	1.7 (−2.7 to 6.1)	0.15	0.48
	SRGI	12.7 ± 8	17.1 ± 10.5	17	3 ± 10.7	2.2 (−1.7 to 6)	0.08	0.53
Total protein (g/day)	Control	64.5 ± 34.5	65.7 ± 61.6	31	−1.3 ± 65.2	2 (−26.4 to 30.3)
	LS	71.4 ± 37.7	78.3 ± 29.5	28	4.6 ± 32.7	7.6 (−18.3 to 33.5)	0.64	0.08
	LBGI	72.8 ± 30.2	71.1 ± 30.8	13	−8.4 ± 23	6.9 (−26.4 to 40.2)	0.74	0.07
	SRGI	70.4 ± 34.6	68.1 ± 21.7	19	−6.5 ± 34.5	−4.7 (−32.7 to 23.4)	0.60	−0.09
Total fat (g/day)	Control	56.7 ± 31.3	62.6 ± 70.5	31	7.3 ± 67.1	19.6 (−11.6 to 50.9)
	LS	66.8 ± 43.3	64.7 ± 30.6	28	−6.9 ± 33.8	12 (−16.9 to 40.8)	0.58	−0.09
	LBGI	61 ± 24.2	74.3 ± 46.8	13	6.9 ± 54.1	31.7 (−4.5 to 68)	0.47	0.16
	SRGI	57.5 ± 32.8	52.6 ± 28.1	19	−10.6 ± 33.3	1.4 (−29.7 to 32.5)	0.21	−0.23
Healthy Eating Index	Control	50.9 ± 11.4	49.7 ± 10.2	31	−2 ± 9.8	−2.7 (−6.7 to 1.4)
	LS	52.1 ± 9.6	55.9 ± 9.9	27	4.5 ± 11.6	4 (−0.3 to 8.4)	0.02	0.59
	LBGI	53.4 ± 13.2	53.8 ± 11.4	13	1.7 ± 16.9	1.4 (−4.6 to 7.3)	0.26	0.36
	SRGI	54.5 ± 10	56.1 ± 12.8	19	1.1 ± 15.3	3.4 (−1.7 to 8.4)	0.05	0.54
Glycemic load	Control	111.3 ± 41.9	120 ± 94.1	30	9.1 ± 77.6	6.6 (−17 to 30.1)
	LS	112.7 ± 45.4	116.6 ± 35.8	26	−2 ± 37.7	−0.8 (−26.2 to 24.7)	0.66	−0.11
	LBGI	121.9 ± 62.7	116.6 ± 55.9	13	−21.8 ± 69.1	−15.9 (−51.1 to 19.2)	0.29	−0.35
	SRGI	104.5 ± 49	100.9 ± 50.7	17	−10.5 ± 53.9	−12.5 (−43.1 to 18)	0.30	−0.30
Glycemic index	Control	59.3 ± 4.1	58.6 ± 5	30	−0.7 ± 6	−0.3 (−2 to 1.3)
	LS	58.6 ± 4.5	58.4 ± 4.3	26	−0.1 ± 5.8	−0.2 (−2 to 1.5)	0.95	0.02
	LBGI	57.4 ± 5.3	54.4 ± 3.5	13	−3.7 ± 5.6	−4.1 (−6.7 to −1.6)	0.01	−0.84
	SRGI	58.5 ± 5	56.1 ± 4.3	17	−2.4 ± 5.6	−2.5 (−4.7 to −0.3)	0.12	−0.48
Physical activity^c
Sedentary behavior (min/day)	Control	1,085.5 ± 106	1,099.4 ± 122.4	40	18.7 ± 102.1	22.1 (−16.7 to 61)
	LS	1,063.4 ± 79.9	1,043.2 ± 108.5	30	−25 ± 97.2	−27.6 (−71.5 to 16.3)	0.07	−0.41
	LBGI	1,022.3 ± 66.4	985.4 ± 165.4	17	−39.3 ± 168.1	−48.9 (−105.3 to 7.5)	0.04	−0.59
	SRGI	1,047.9 ± 81.3	989 ± 95.1	21	−64 ± 88.8	−65.5 (−116.4 to −14.6)	0.004	−0.73
Light activity (min/day)	Control	21.6 ± 8.7	21.4 ± 12.3	40	−1.2 ± 12.1	−1.8 (−8.2 to 4.7)
	LS	22.8 ± 5.1	23.9 ± 12.5	30	1.6 ± 12	2.6 (−3.7 to 8.9)	0.14	0.23
	LBGI	28.5 ± 10.5	27.9 ± 12.7	17	−0.8 ± 9.1	0.6 (−7.1 to 8.3)	0.51	0.13
	SRGI	22.9 ± 5.2	30.6 ± 13.9	21	7.5 ± 15.7	5.2 (−1.6 to 11.9)	0.03	0.38
Moderate activity (min/day)	Control	52.4 ± 17.8	48 ± 20.7	40	−6.6 ± 18.8	−7.5 (−17.2 to 2.2)
	LS	55.3 ± 9.4	55.2 ± 20.6	30	0 ± 18.3	2.3 (−7.2 to 11.8)	0.03	0.34
	LBGI	66.7 ± 14.6	62.6 ± 18.6	17	−4.4 ± 12.6	−2.6 (−14.3 to 9)	0.37	0.18
	SRGI	56.3 ± 14.1	65.8 ± 18.9	21	9.3 ± 21.2	7.1 (−3.1 to 17.3)	0.003	0.53
Vigorous activity (min/day)	Control	255.1 ± 86	225.6 ± 90.2	40	−36.7 ± 63.8	−44.2 (−78.9 to −9.4)
	LS	271.4 ± 60.7	266.2 ± 73.8	30	−10.3 ± 65.7	−7.4 (−41.4 to 26.5)	0.03	0.36
	LBGI	298.4 ± 40.1	278.2 ± 64.7	17	−19.4 ± 56.8	−24 (−65.4 to 17.4)	0.28	0.20
	SRGI	279.9 ± 64.4	297.8 ± 66.9	21	19.6 ± 59.6	13.3 (−23.3 to 49.8)	0.001	0.58
Moderate + vigorous activity (min/day)	Control	307.5 ± 102.1	273.6 ± 108.4	40	−43.3 ± 81.4	−51.6 (−95.3 to −7.8)
Moderate + vigorous activity (min/day)	LS	326.7 ± 67.8	321.4 ± 92.9	30	−10.3 ± 82.1	−4.9 (−47.5 to 37.8)	0.02	0.36
	LBGI	365.2 ± 46.7	340.8 ± 76.5	17	−23.8 ± 68.2	−27.1 (−79.2 to 25)	0.30	0.20
	SRGI	336.2 ± 77.2	363.6 ± 82.6	21	28.9 ± 79.3	20.6 (−25.3 to 66.6)	0.001	0.58

Difference score among participants with data for baseline and 3-month assessment. Participants' missing data for baseline and/or 3-month assessments are not included in the table.

Estimated marginal mean for change (difference score). Analyses nested in school. Adjusted for a priori baseline measurement.

Mean number of minutes per day across 7-day observation period.

GI, guided imagery; LBGI, lifestyle behavior GI; LS, lifestyle education; SRGI, stress reduction GI.

Adverse events

The intervention was well tolerated with relatively few adverse events, only four of which were categorized as serious adverse events (one event each of pain in hands and feet, appendicitis, torn knee ligament, and suicidal ideation), none of which were deemed related to the protocol.

Discussion

The Imagine HEALTH intervention sought to determine the effects of group GI added to a didactic, health-promoting lifestyle curriculum, with primary outcomes of physical activity behaviors, while also assessing dietary intake. To the best of the authors' knowledge, this is the first fully powered RCT lifestyle intervention studying the effect of GI on obesity-related lifestyle behaviors in an adolescent population. There is also little to no literature on the uses, acceptability, and cultural relevance of GI in a Latinx adolescent population beyond the authors' prior studies, which demonstrated feasibility, acceptability, and efficacy in this population despite their being mostly naive to mind–body modalities.^11,21 The relaxation and positive imagery that is encompassed in GI is thought to attenuate psychoneuroendocrine pathways that affect the stress response.²⁸ Beyond stress reduction, GI and related mind–body therapies have also been used to promote behavior change in adults with eating disorders and obesity.^29
–31 The authors reasoned that GI may offer a developmentally appropriate behavioral therapy in teens, in that it involves affective components known to influence adolescent behaviors, as well as elements of mindfulness.^32

–35

The ITT analysis showed no group differences in sedentary behavior or physical activity and showed significant improvement in the HEI only in the LS education group. Therefore, the primary analysis did not support the hypothesis that GI would augment intervention effects on obesity-related lifestyle behaviors. The nutrition curriculum focused on improving carbohydrate quality^8,36 from simple, refined sugars to complex carbohydrates and fiber, which has demonstrable health benefits for Latinx teens,^16,37 combined with the process of intuitive eating,²⁰ and is fully consistent with pediatric and adolescent dietary guidelines.¹³ Intuitive eating promotes a healthy nonrestrictive relationship with food through the utilization of hunger and fullness cues and promoting eating satisfaction,²⁰ and studies have linked it to good health outcomes in young adults.^18,19 To the best of the authors' knowledge, this is the first time intuitive eating has been used in a specific lifestyle intervention, although the similar concept of mindfulness-based eating has been used successfully in dietary interventions in adults.^38,39 The present study design does not allow us to determine which specific intervention components mediated the change seen in the HEI, but supports future research to determine the specific effects of these approaches to healthy eating in adolescent populations.

The sensitivity analysis, showing additional positive lifestyle behavior changes for adherent participants, suggests that poor adherence obscured potential benefits of this intervention. The findings of decreased sedentary behavior and increased MVPA are consistent with the pilot findings using individualized (i.e., nongroup) GI.¹¹ The greatest decrease in sedentary activity and increase in MVPA were observed in the SRGI group, conforming to the hypothesis that GI would augment the outcomes occurring from didactic lifestyle education alone, but in contrast to the expectation that the LBGI intervention would be the most efficacious. This suggests that the LBGI imagery content meant to promote healthy dietary and physical activity behaviors may be overly complex and more difficult to deliver in group than the more straightforward SRGI. The nonspecific effect of SRGI on lifestyle behaviors may have been achieved by teaching teens a way to balance and center that could subsequently lead to improved real-time behavior choices, or improved attention to the didactic education elements of the program. This is important in considering future interventions since in our experience SRGI was easier to conceptualize and deliver than the LBGI curriculum and represents a therapeutic modality that can potentially be learned and used relatively easily by primary care providers to augment conventional allopathic practices.

In terms of dietary outcomes, the sensitivity analysis replicated the ITT finding of improvement in the HEI in the LS group, without an additional effect from the GI. GI did decrease the glycemic index in the LBGI group (large effect, d = 0.84) and the SRGI group (moderate effect, d = 0.48), without change in the LS group. This could be important since a low glycemic index diet has been effective in both adolescents with obesity⁹ and adults with diabetes,^40,41 and future work could seek to confirm this finding.

Participant adherence was suboptimal in all intervention groups. Thus, a majority of the participants did not receive the intended “dose” of intervention, limiting the capacity to interpret negative findings. This occurred despite our: (1) recognizing this challenge in an adolescent study population facing a high study burden; (2) substantial efforts to boost attendance throughout the conduct of the intervention; and (3) pilot intervention suggesting that we would be able to meet adherence goals.²¹ However, the pilot was limited to 6 weeks, and in the current study, the authors clearly saw a drop in attendance in the latter half of the full 12-week intervention. The interactions with participants did not suggest that this was due to loss of interest in the intervention in these latter weeks, but was rather linked to increasing intensity of school demands and approaching final examinations toward the end of the intervention. Changes in the future to improve adherence could include limiting the program to a maximum of two afternoons a week, supported by the higher adherence rate in the LS group (two sessions per week versus three sessions per week in SRGI and LBGI), shortening the intervention to 6–8 weeks, delivering the intervention during required classroom time, or delivering parts of the intervention remotely using technological platforms. Beyond the poor adherence issue to explain the modest findings of lifestyle behavior change in the ITT analysis immediately upon completing the intervention, it may be that effects may yet be seen after a longer period of time, as other lifestyle intervention studies in adolescents have shown changes only after 6–12 months of intervention.^36,10,42,43

Strengths of this study include the fact that this was a well-designed RCT using a mind–body modality in a highly innovative, safe, lifestyle intervention. The authors worked with a greatly understudied adolescent population subjected to great health disparities and approached the intervention from the standpoint of promoting healthy lifestyle behaviors in a population of youth of all body sizes. The authors utilized robust study methodologies and recruitment procedures, which included collaboration with outside community groups and the local school district to deliver the intervention, along with rigorous outcome measures (accelerometry and multiple dietary recalls).¹² The primary limitation of the study was the poor participant adherence, thereby limiting the degree to which conclusions can be made regarding the effectiveness of GI in this study. Generalizability of results is uncertain beyond the predominantly Latinx, lower socioeconomic, adolescent study population. Finally, although physical activity was objectively measured using wrist-worn accelerometers, interpreting the results by the absolute amount may be misleading, given the challenges related to the accuracy of classifying data from wrist-worn accelerometer collected in free-living environment.⁴⁴ Therefore, the current study interpreted the findings in terms of the magnitude of change before and after the intervention.

In conclusion, the Imagine HEALTH lifestyle intervention did not show an effect of GI on lifestyle behaviors in the primary ITT analysis. Subsequent post hoc analyses of adherent participants did suggest that GI can amplify the role of didactic lifestyle education for sedentary behavior and physical activity. Future attempts at similar interventions must account for the difficulties encountered in delivering such a complex holistic intervention to an adolescent population.

Footnotes

Authors' Contributions

All coauthors have reviewed and approved the article before submission. M.J.W.: Study conceptualization/design; methodology; investigation; supervision; funding acquisition; drafting initial article; review/editing article. Q.A.: Investigation; supervision; funding acquisition; review/editing article. D.S.-M.: Study conceptualization/design; methodology; investigation; supervision; funding acquisition; review/editing article. J.N.D.: Methodology; supervision; review/editing article. C.K.F.W.: Methodology; investigation; supervision; drafting initial article; review/editing article. K.G. and M.P.: Investigation; review/editing article. N.B.W.: Data curation; formal analysis; drafting initial article. L.D.: Data curation; formal analysis; review/editing article. C.J.L.: Data curation; formal analysis; drafting initial article; review/editing article.

Acknowledgments

The authors would like to acknowledge the collaboration of the nonprofit group SOS-Mentor and their commitment to improving eating and exercise behaviors among youth, the administration, and staff of the involved high schools and LA Unified School District, and the nutrition departments of Pepperdine College and California State University Los Angeles. The authors are grateful to their hardworking research staff and the many students at all academic levels who took part in this work. The authors would especially like to thank the students who took part in this study, and their families, for their participation and for teaching us so much.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This work was sponsored by the National Institutes of Health (NIH) National Center for Complementary and Integrative Health, R01AT008330, and supported by grants UL1TR001855 and UL1TR000130 from the National Center for Advancing Translational Science (NCATS) of the U.S. NIH. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Supplementary Material

Supplementary Data

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