Pounds Off Digitally Study: A Randomized Podcasting Weight-Loss Intervention

Introduction 

In the United States, 66.3% of adults are either overweight or obese (BMI>25 kg/m2)1 and are at a significantly higher risk of developing many chronic diseases.2 The main treatments for overweight and obesity include dietary changes, increases in physical activity, and other behavioral modifications.3 Technology-enhanced approaches to weight loss have begun to emerge with the increased development of electronic media. Many researchers are now using the Internet to deliver interventions.4 These interventions, however, often lack portability, restricting where and when interventions can be delivered. Web-based interventions typically also require participants to be literate and capable of effectively processing written information.

The increased prevalence of overweight5 has occurred concomitantly with an increase in “screen time”—which is the use of computers, televisions, and video games—by both children and adults.6 In contrast, podcasts can be listened to while mobile. Because many adults and children are spending increased amounts of time in front of screens or connected to the Internet,7 it may be important to use portable media in weight-loss interventions to avoid increased screentime further.

An emerging new portable technology is podcasting, a term that came into existence in 2004.8 Despite the growing popularity of podcasting (audio files for a portable music player or computer), little is known about its use in promoting weight loss. Podcasting represents a largely untapped conduit for providing weight-loss information to people with Internet access or those who do not want to participate in face-to-face weight-loss interventions, which can be seen as time consuming and often inconvenient.9

Results 

The flow of participants through recruitment, intervention, and follow-up can be found in Figure 2. Of the 120 volunteers who inquired about the study between September 2007 and January 2008, 94 (78%) were enrolled in the study; ten (8%) declined participation; and 16 (13%) did not meet inclusion criteria. Of the 94 who were accepted into the study, 16 (17%) did not attend the introductory meeting (nine in the control group and seven in the enhanced group), and therefore randomization was not revealed and no data were collected on these participants; thus, they are not included in the intention-to-treat analysis. There were no significant differences in baseline characteristics between completers and noncompleters. Table 2 outlines baseline demographics. The control and enhanced groups did not differ significantly across any of the variables except that there were a disproportionately greater number of subjects in the control group without a graduate degree. A linear regression was conducted using baseline weight to predict follow-up weight, adjusting for gender and group, as well as education and group. There was no effect of education (β=−0.03, p=0.16) or gender (β=−0.19, p=0.85). Of those participants who reported having previously downloaded a podcast, only one participant (in the enhanced podcast group) reported being currently subscribed to a weight-loss–related podcast.

View Large Image Download to PowerPoint

Figure 2. Participant recruitment and analysis flow diagram

Table 2. Baseline demographic data for control and enhanced podcast group participantsa

		Control group	Enhanced group
	n	37	41
	Age (years; M±SD)	39.6(±12.2)	37.7(±11.8)
	Gender
	Male	7(19)	13(32)
	Female	29(81)	28(68)
	Race/ethnicity
	Black	6(17)	5(13)
	White	28(78)	35(85)
	Other	2(5)	1(2)
	Hispanic
	Yes	4(11)	2(5)
	No	32(89)	39(95)
	Marital status
	Not married	19(43)	19(47)
	Married	17(47)	22(53)
	Education
	High school, partial or graduate	11(31)	8(20)
	College, partial or graduate	18(50)	15(37)
	Graduate degree	7(19)	18(43)
	Occupation
	Unemployed	0(0)	2(5)
	Service occupation	4(11)	1(2)
	Technical, sales, administrative	11(31)	8(20)
	Professional, specialty	8(22)	14(34)
	Executive, managerial	1(3)	6(15)
	Retired	1(3)	1(2)
	Student	11(31)	9(22)
	Number of years participant has owned an MP3 player (M±SD)	2.0(±2.0)	1.8(±1.7)
	Hours a day spent online (M±SD)	4.1(2.7)	4.7(±3.1)
	Participants who had previously downloaded a podcast (n [%])	15(42)	26(63)
	Podcasts to which participants are currently subscribed (M±SD)	2.8(±1.8)	2.5(±1.5)

a Data are M (±SD) or n (%) unless otherwise indicated.

Table 3 outlines the results of weight, diet, physical activity, and knowledge changes. Results below are presented as mean±SD. Participants in the enhanced podcast group had a greater decrease in weight (−2.9±3.5 kg) and BMI (−1.0±1.2 kg/m2) compared with the control group (−0.3±2.1 kg and −0.1±0.7 kg/m2; p<0.001 between groups). The enhanced group also reported greater increases in fruit (reported 0.4±0.7 increase in consumption category) and vegetable (reported 0.2±0.9 increase in consumption category) intake than the control group (change of 0.01±0.4 for fruit and −0.2±0.7 for vegetables; p<0.05 for both categories for between groups). There was no change in high-fat-food intake in either group. There was also no significant difference between groups with regard to reported moderate activity, walking, or sedentary behavior changes. There was, however, a difference in reported vigorous activity, with a greater increase in the number of days participants engaged in vigorous activity seen in the enhanced group (increase of 0.8±0.9 days/week) as compared to the control group (decrease of −0.4±1.4 days/week; p<0.01 between groups). Participants in the enhanced group also saw a greater increase in the weight-loss knowledge scores as compared to the control group. There were no significant differences between groups or within groups with regard to changes in the SCT constructs.

Table 3. Differences between groups in weight, food group intake, physical activity, and knowledge during study perioda

		Control group (n=36)	Enhanced group (n=41)	p-value for difference between groups
	Weight (kg)
	Baseline	89.0±13.6	91.9±15.0
	12 weeks	88.7±13.9	89.0±13.6
	Difference	−0.3±2.1	−2.9±3.5	<0.001
	BMI (kg/m2)
	Baseline	31.4±4.1	31.8±3.2
	12 weeks	31.3±4.3	30.8±3.4
	Difference	−0.1±0.7	−1.0±1.2	<0.001
	Vegetables-consumption categoryb
	Baseline	2.4±0.6	2.3±0.7
	12 weeks	2.6±0.7	2.6±0.7
	Difference	0.01±0.4	0.4±0.7	<0.05
	Fruits-consumption categoryb
	Baseline	2.9±0.8	2.5±1.0
	12 weeks	2.7±0.6	2.7±0.7
	Difference	−0.2±0.7	0.2±0.9	<0.05
	Fatty foods–consumption categoryb
	Baseline	2.1±0.5	2.1±0.5
	12 weeks	1.9±0.5	1.8±0.5
	Difference	−0.2±0.4	−0.3±0.4	0.14
	Vigorous activity (days/week)
	Baseline	1.8±1.8	1.2±1.4
	12 weeks	1.4±1.6	2.1±1.9
	Difference	−0.4±1.4	0.8±0.9	<0.01
	Moderate activity (days/week)
	Baseline	1.6±1.9	1.3±1.6
	12 weeks	1.9±2.2	2.2±2.0
	Difference	0.3±2.2	0.9±2.0	0.22
	Walking (days/week)
	Baseline	4.3±2.2	3.8±2.5
	12 weeks	4.5±2.3	4.6±2.2
	Difference	0.2±2.2	0.7±2.0	0.29
	Sitting (hours/day)
	Baseline	9.5±6.1	9.0±3.2
	12 weeks	9.2±6.2	8.2±3.8
	Difference	−0.3±8.7	−0.8±4.8	0.73
	Knowledge scorec
	Baseline	28.1±7.3	31.3±7.1
	12 weeks	30.5±7.8	36.8±4.7
	Difference	2.4±5.2	5.4±6.5	<0.05

a All data are mean±SD. b Possible score range=1–5 c Possible score range=6–42

Table 4 outlines the results of hypothesized communication mediators and adherence data collected. There were significant differences between groups in all of the variables related to the hypothesized communication mediators, including greater elaboration; user control; and satisfaction with the intervention and less cognitive load (where a higher score means less cognitive load). Of the 24 episodes available, participants reported listening to an average of 16.6±7.5 in the control group and 17.5±8.1 in the enhanced group (p<0.67). Participants were asked at 12 weeks about their listening behaviors during the study. The majority of participants reported listening to podcasts at home most often (53.7%); followed by in their office and at work (20.9%); or while walking or exercising (13.4%). Most participants reported being sedentary while listening to the podcasts, either sitting at their desk (44.8%) or sitting at home (22.4%). Slightly more than 50% of the participants reported listening to the podcasts on their computer (52.2%) versus a portable MP3 player. The majority of participants did not listen to any other weight-loss– or health-related podcasts during the study (85%). There was no significant difference between groups with regard to these variables.

Table 4. Differences between groups in elaboration, user control, cognitive load, and intervention perception at 12 weeksa

		Control group (n=37)b	Enhanced group (n=41)b	p-value for difference between groups
	Elaboration scorec	24.7±15.4	41.3±12.3	<0.001
	User control scored	40.6±16.0	53.6±12.9	<0.001
	Cognitive load scoree	6.5±4.1	10.6±3.1	<0.001
	Intervention perception scoref	11.2±7.1	17.4±5.1	<0.001
	Number of podcasts (of 24) participants reported they listened to during the study	16.6±7.5	17.5±8.1	0.67

a These questionnaires all used a 7-point Likert-type scale. b All data are M±SD. c Possible score range=9–63 d Possible score range=10–70 e Possible score range=2–14 f Possible score range=3–21

Discussion 

An enhanced, theory-based podcast produced greater weight loss, user control, and elaboration and less cognitive load than a general weight-loss podcast. Participants in this study were able to achieve a modest weight loss by listening to a carefully designed, theory-based podcast on weight loss. These results were achieved with minimal face-to-face interaction—participants received all their information on weight loss via the biweekly podcast. A mean 6-month weight loss of 7.9 kg was reported in a meta-analysis of 16 mostly face-to-face weight-loss interventions using diet and physical activity.19 This rate of weight loss (approximately 0.3 kg/week), however, is slightly higher than the rate of weight loss seen in the present study (approximately 0.2 kg/week). Participants in the enhanced podcast group reported greater increases in fruit and vegetable intake than control participants, but no change in intake of high-fat foods. The enhanced podcast intervention emphasized reducing calories through favoring low-fat foods, fruits, and vegetables and also encouraged participants to increase physical activity—mainly through daily walking. Participants in the enhanced group reported greater vigorous activity compared to the control group; however, they did not report an increase in walking or moderate activity. The control podcast focused mostly on cognitive restructuring and did not regularly discuss specific diet and physical activity recommendations. This may have been one of the reasons the control podcast group saw so few changes in these outcomes.

Whereas the podcast based on SCT proved to be effective in producing a weight loss of 2.9 kg, in this study, the weight loss achieved in the control podcast group was minimal (0.3 kg). Theory-based weight-loss interventions using other technologies have also been shown to be effective.20 Concepts from SCT, such as outcome expectations (what the participant expects will occur when he or she attempts to lose weight); expectancies (the value a participant places on weight loss); and self-efficacy were all used in the present study to increase weight loss and deliver health information. No differences in these constructs were seen between or within groups. These constructs were each assessed with one item and that may not have been sensitive enough to assess differential changes in the groups. In addition, 12 weeks may not have been enough time to produce significant changes in these constructs. As hypothesized, participants in the enhanced group had greater increases in reported knowledge on weight-loss topics. The enhanced podcast also included a continuing soap opera, which was an entertaining way to provide additional information on healthy eating and exercise, and may have accounted for the greater participant recall.

Participants in the enhanced group reported greater elaboration, suggesting that participants used the central route to process the information in the podcasts, which should lead to an enduring behavior change.21 Participants also reported greater user control. Although both podcast groups accessed the audio files in similar ways (on portable MP3 players or on their computers), the enhanced group reported a greater sense of control over learning pace and navigation, which should allow for better and more effective learning.10 The enhanced podcast also produced less cognitive load than the control podcast, which should lead to participants' being better able to retain the material presented in the podcasts.12, 13 The enhanced podcast followed the same format every week, and perhaps this allowed the participants to have a sense of structure in their weight-loss efforts, and reduced cognitive load. The format of the control podcast varied between episodes. The enhanced podcast group also reported greater satisfaction with the intervention. This greater satisfaction could have resulted from participants in the enhanced group achieving more weight loss; however, research participants who feel more satisfaction with the intervention may achieve better weight loss.22 Thus, it appears that communication variables, such as elaboration and user control, may help explain the differential effects of the two podcast interventions.

Although the majority of participants reported being sedentary—either sitting at home or at work—while listening to the podcasts, the podcasting mode of delivery at least allowed participants mobility, and in fact 13.4% were walking or exercising while listening. More than half of all participants regularly listened to the podcasts on a computer instead of a portable media player, which is a similar finding to that of a survey on podcasting behavior.23 Desktop computers were the most common device (80%), followed by portable media players (66.1%).23 This survey also found results similar to those of the present study, with the majority of respondents reporting listening to podcasts mostly at home (79%).23

There were several strengths of the present study. These included a randomized design and an intention-to-treat analysis. The results are likely to be applicable outside the research setting because participants received minimal face-to-face intervention, prepared all their own meals, and found their own ways to increase physical activity. The intervention was also very low-cost and would be easy to disseminate. There were also several limitations to the study. The participant sample for this study was mostly white and highly educated. Dietary data were measured using a brief questionnaire instead of more detailed methods, such as a 24-hour recall or food record.24 Physical activity was also measured using a questionnaire, but less-subjective methods, such as a pedometer, may have provided more-accurate results.25 Also, this was a short-term intervention with modest weight loss, and therefore, it is unknown whether the weight loss seen in this study would be maintained over the long term. Despite the use of a randomized design, the groups had unequal numbers of men and those with graduate degrees. Although this was not a significant difference, this inequality is a limitation.

Finding new and innovative ways to reach people who wish to lose weight is important. This study found that podcasting may be an effective way to deliver health interventions and produce behavior change. This study demonstrated that podcasts can be more effective when they are theory based and carefully designed to promote cognitive processing and elaboration of information. Future studies should find ways to encourage participants to be more mobile while listening to the podcasts—such as encouraging participants to listen to the podcasts on portable players during exercise—in order to increase physical activity. Long-term studies should also be carried out to see if the podcasting of weight-loss information and encouragement can produce long-lasting effects or if combining podcasts with other features of an Internet intervention (monitoring, feedback, and support) might enhance weight losses resulting from information delivered in either modality alone. Finally, additional research should also be conducted to see if these results can be replicated in other populations.