. 2023 May 25;11:e39649. doi: 10.2196/39649

Table 1.

Study characteristics.

Study and year	Location, N, and design	Sex (%)	Age (years)	Health targets and measures	Technology and procedures	Outcomes
Echeazarra et al [17], 2021	Location: Spain N=112 Design: 2-year RCT^a	Female: 42	Mean 52.1	BP^b	Tensiobot (telegram app) Reminders to check BP Education on how to properly check BP using videos Warnings and graphic feedback on BP GPs^c can connect with the app to access patient data Advice offered 24/7	No significant differences in adherence between groups Bot group had higher levels of knowledge on good practice skills for BP (t=2.11; df=82.3; 95% CI 0.39-12.6; P<.05) Measurements (P<.05) Bot found to be acceptable/likable Adherence after intervention: 85%
Griffin et al [19], 2021	Location: United States N=15 Design: mixed methods questionnaires with semistructured interviews qualitative	Female: 53	Mean 59 (SD 11)	BP	Theoretical discussion around chatbots for hypertension medication management	Most patients were interested in and open to trying a chatbot for hypertension medication management and reminders Privacy concerns and usability with mobile phones
Larbi et al [20], 2021	Location: Switzerland N=30 Design: feasibility study	Female: 50	Range 18-69	PA^d	MYA social media chatbot	Perceptions of usefulness and informativeness: 53% User friendly: 83% Failed to understand user input: 63.3% Potential confusion with using the technology 43.3%
Lin et al [27], 2021	Location: Taiwan N=96 Design: factorial experimental study with 4 arms	Female: 53	Mean 21.5; range 18-42	PA (core muscle exercise)	VR^e avatar	Increase in PA (vector movement) of 986.7 (SD 1.03) points in in normal realistic avatar relative to muscular avatar Higher self-efficacy for core muscle exercise in normal avatars vs muscular avatars in female participants (+0.66, SD 0.1 points) and higher levels than in male participants (+0.9, SD 0.2 points) P<.05
Dol et al [37], 2021	Location: The Netherlands N=71 Design: qualitative study	Female: 100	Mean 44.4 (SD 12.86); range 19-70	Emotional eating	Conversational coach for emotional eating	The design of the conversational coach should integrated dialectal behavioral coaching strategies, as preferred by participants with emotional eating behavior
Lin et al [27], 2021	Location: Taiwan N=104 Design: experimental design study	Female: 50	Mean 70.39 (SD 6.51); range 60-88	PA perceived exertion Self-efficacy	Assigned to either age-matched or young avatars for PA Theory: Proteus effect of avatar embodiment Watched videos in a digital gym where they exercised Wore a head-mounted display	Older male participants assigned to young avatars had higher perceived exertion than counterparts assigned to older ones (+1.56, SD 0.31 points; male participants only) Female participants assigned to young avatars had higher self-efficacy for future exercise than counterparts (+0.45 points) and male participants P<.05
Maher et al [13], 2021	Location: Australia N=31 Design: proof-of-concept study	Female: 67	Range 45-75	PA, Mediterranean diet, and weight	AI^f Paola chatbot teaches users about exercise and uses BCTs^g, including goal setting, self-monitoring, and feedback	Mean increase in diet score: 5.7 (95% CI 4.2-7.3) Mean PA increase: 109.8 min (95% CI 1.9-217.9; P<.01) Mean weight loss: 1.3 kg (95% CI −2.5 to −0.7; P<.05) P<.01 No significant changes in blood pressure
Hickman et al [40], 2021	Location: United States N=109 Design: 2-arm RCT	Female: 59	Mean 52 (SD 11)	Hypertension, quality of the physician-patient interaction	Avatar intervention or video on hypertension management	Scores for the quality of the patient-provider interaction were better over time (F3=5.25; P<.01) in the within-subjects analysis along with a time by experimental condition interaction (F3=2.91; P<.05) Between-subject effects per treatment were insignificant No significant changes in blood pressure
Napolitano et al [49], 2021	Location: United States N=136 Design: feasibility study (12 weeks)	Female: 100	Mean 27.8 (SD 5.4)	Weight, diet, and PA; exercise self-efficacy	Conversational coach gave lessons on health behaviors	No significant results were found for differences in weight, PA, or consumption of fast food between the intervention arm and control groups High attrition 44% Goal achievement for nutrition <10%
Santini et al [55], 2021	Location: Austria, Italy, and Netherlands N=60 (2 waves) Design: qualitative study with focus groups and phone interviews	Female: 53.3% wave 1; 51.6% wave 2	Mean 61.9	Health behaviors, diet, and PA	Embodied coach for diet and PA	Desire for the avatar to motivate older adults to exercise Supportive tone and language that is not authoritarian or patronizing
Krishnakumar et al [44], 2021	Location: India N=102 Design: pre-post intervention (1 arm) 16 weeks	Female: 31.4	Mean 50.8	Diabetes (blood sugar), diet, PA, and weight (logged)	Wellthy CARE mobile app	The use of the Wellthy CARE digital therapeutic for patients with T2D^h showed a significant reduction in the mean levels of HbA_1cⁱ −1.16% (95% CI −1.40 to −0.92; P<.01); FBG^j (−11 mg/dL), and PPBG^k (−22 mg/dL); P<.05 Weight decreased by 1.32 kg (95% CI −0.63 to −2.01 kg) after 16 weeks
Dhinagaran et al [36], 2021	Location: Singapore N=60 Design: one arm web-based feasibility stud	Female: 62	Mean 33.7	Diet, PA, sleep, and stress	Chatbot for diabetes prevention, diet, exercise delivered over Facebook Messenger (Meta Platforms Inc)	Engagement: 50% Retention: 93% Satisfaction: high at 92% 50% agreed that the chatbot was acceptable and usable No significant changes in health behaviors including PA Minimal improvement in diet: increase in fruit intake (3 portions) by 4% and vegetables once per day by 2%
To et al [61], 2021	Location: Australia N=116 Design: quasi-experimental study (6 weeks)	Female: 81.9	Mean 49.1 (SD 9.3)	PA	Fitbit plus a chatbot in the Messenger app	Usability score: 89.4% Desire to continue using: 35.4% Helped them: 53% Mean PA increase: 154.2 min/week (95% CI 2.28-5.63) OR for meeting PA guidelines: 6.37 (95% CI 3.31 to 12.27) Mean steps/day increase: 627 (95% CI 219 to 1035)
Mitchell et al [48], 2021	Location: United States N=158 Design: mixed methods survey with qualitative interviews study	Female: 100	Mean 56 (SD 11) intervention; 57 (SD 11) control	Diabetes	Avatar for diabetes self-management	Avatars provide support for diabetes self-management via 3 areas (self, social, and physical) that are linked with engagement
Strombotne et al [58], 2021	Location: United States N=590 Design: quasi-experimental study	Female: 11	Mean treatment=58.1; control=57.7	Diabetes and risk factors	Conversational coach and ketogenic diet	BP decrease (systolic): 1.4 mm Hg (95% CI −2.72 to 0.14) Diastolic BP levels decreased: −1.43 (95% CI −2.72 to −0.14) mm Hg HbA_1c decreased: −0.69 (95% CI −1.02 to 0.36) Diabetes medication fills: −0.38 (95% CI −0.49 to −0.26) BMI: −1.07 (95% CI −1.95 to −0.19) kg/m²
Alves Da Cruz [31], 2020	Location: Brazil N=27 Design: cluster randomized crossover trial	Female 48.1	Mean 63.4 (SD 12.7)	HR^l, BP, and RR^m	Avatars with exergames for PA in patients undergoing cardiovascular rehabilitation	Increase in HR (z=82.8; P<.01) and RR (z=12.9; P<.01) during and (5 min) after exergame Changes in systolic BP but not diastolic with differences within moments z=11.26 (P<.01) With no statistical significance between groups
Kowalska et al [43], 2020	Location: Poland N=249 Design: cross-sectional study	Female: 36.5	Mean 65.3 (SD 13.8)	CVDⁿ	Telehealth voice technology with health professionals and voice conversational agent	High desirability for telehealth consultations with a cardiologist combined with a conversational agent Desirability for telemonitoring of vitals: 67.5% 70.7% wanted a consultation with a cardiologist remotely
Piao et al [51], 2020	Location: South Korea N=106 Design: Exploratory Randomized Controlled Trial 12 weeks	Female: 56 intervention; 57 control	Range 20-59	Health behaviors (diet and exercise); SRHI^o	Lifestyle coaching chatbot Informed by habit formation Cues and goals	Significant improvement in health behavior The intervention group had higher scores on the SRHI of 7.12 (SD 5.57) with P<.05 at 4 weeks; no significant differences between groups at 12 weeks, PA remained higher after 12 weeks (P<.05)
Naylor et al [50], 2020	Location: United States N=20 Design: pilot study	N/A^p	Mean 8.4 (SD 1.3)	VO₂ (mL × kg^–1 × min^–1) using indirect calorimetry questionnaire on liking and motivation	Children played tennis with their friend and an avatar	Increased VO2 during game play in both cooperative (3.8 + 1.8 mL × kg^-1 × min^-1) and competitive play (4.4 +1.8 mL × kg^-1 × min^-1) compared with resting condition (P<.01) Children liked exercising more in cooperative games than in competitive games (P<.01) No differences between game styles in motivation for PA (P>.05)
Hahn et al [39], 2020	Location: United States N=42 (child and parent dyads [n=40 completed baseline and follow-up measures]) Design: pilot intervention	Female (children): 55.2	Treatment: mean 8.06 (SD 1.10); control: mean 7.5 (SD 1.38)	PA using Fitbit and self-report on motivation for PA	Children wore Fitbit with a personalized dog avatar for socializing and support (digital fitness kiosk); theory informed (social cognitive theory)	Completion rate: 81.63% Mean number of PA goals reached: 3.28 Mean time playing with pets: 20.35 min Mean number of active min: 66 min (no statistical significance was found)
Navarro et al [24], 2020	Location: United States N=305 Design: 3-arm RCT	Female: N/A	Mean 20.0 (SD 2.2); range 18-37	Cardiac frequency, step counts, accelerometer, and HR monitor	Randomly assigned to avatars embodying them (same face) or different from them (strangers) Avatars wore normal clothes or gym clothes	Higher cardiac output (frequency) from 6 to 12 min in users of avatars that had a similar appearance (face) Higher output in users with avatars that additionally wore sports clothing at 6-7 and 10-minute periods Support for the Proteus effect hypothesis No changes in step count
Davis et al [16], 2020	Location: Australia N=28 Design: pilot single-arm study	Female: 68	Mean 56.2 (SD 8); range 45-75	Diet: Mediterranean diet adherence tool. Weekly log for diet and step count; activity tracked using a wrist worn tracker (Garmin) that syncs with Paola. Minutes of moderate to vigorous PA assessed with Active Australia Survey	Conversational assistant Paola for diet and PA consisted of educational modules, weekly check-ins, and 24/7 availability for PA and diet questions 12-week pilot	Assisted with increasing PA (step goal achieved 59% of the time) Adherence to diet: 91%
Navarro et al [23], 2020	Location: Spain N=42 Design: 3 arms—2 avatars vs control	Female: 100	Mean 31.9 (SD 11.7); range 19-61	PA, IPAQ^q, self-efficacy to regulate exercise, and PA enjoyment scale (PACES^r)	Avatar: ideal (perfect body) or normal (matching the participant) and web-based intervention without the avatar	Increased PA in all groups (F1,39=15.8; P<.01; web-based intervention effects) No effects of time by avatar assignment, ie, interaction
Balsa et al [32], 2020	Location: Portugal N=20 Design: usability study with qualitative interviews	Female: experts 88.9%; end users 27.3%	Mean 62.62; mean end users 70.9; mean experts 54.3	Usability of the app for diabetes medication adherence and improving lifestyle behaviors, diet, and PA	The conversational coach resembles a human Integrated BCTs: goal setting, self-monitoring, feedback, and social support/counseling	Usability score: 73.75 (SD 13.31) (indicates high usability of the coach)
Chin et al [35], 2020	Location: United States N=15 Design: feasibility study	Female: 60%	Mean 67 (SD 5.84)	PA	Health coach for PA As part of a PA program using a Google Home device (Google LLC)	Usability was high 80% of the participants did not experience challenges when interacting with the conversational coach
Fadhil et al [18], 2019	Location: Italy N=19 Design: validation study (4 weeks)	Female: 42	Mean 28.5; range 19-53	Diet and PA questionnaires via chatbot and motivation (HAPA^s)	CoachAI text based conversational agent Tailored coaching for habits	Participants were satisfied with the agent High trust to share personal information to the coach
Ahn et al [30], 2019	Location: United States N=67 Design: field study (3 days)	Female: 61.19	Mean 11.24 (SD 0.85); range 9-13	PA and basic psychological needs	Use of a digital dog, with and without a points-based reward system	Higher levels of PA in the rewards points group briefly versus control (F1,58=5.32; P<.05) No significant effects on PA over time
Stephens et al [26], 2019	Location: United States N=23 Design: feasibility study	Female: 57	Mean 15.2; range 9.7-18.5	Weight management; pre-diabetes	Tess text-based chatbot counsellor for healthy behavior change usability assessed with progress toward goals and engagement	Usefulness rate: 96% Progress toward goals frequency: 81%
Srivastana et al [57], 2019	Location: United States N=10 Design: usability study	Female: 70	Range 44-67	Prediabetes	The web-based module used to support diabetes prevention education and a mobile app that is an electronic diary and a coach	Success of modules 60% as they meet weight loss of 5% Compliance with dietary recommendations: 59%-87% Compliance with PA: 52%-93%
Thompson et al [59], 2019	Location: United States N=27 Design: pilot feasibility study	Female: 73 (teens)	Range 10-15	Diabetes	Conversational agent with human features Conversations around diabetes education	Attrition: low (<10%) High satisfaction: >80% Technical issues<10% Teens and families had a positive experience
Thompson et al [29], 2018	Location: United States N=48 Design: laboratory-based study	Female: 50	Range 12-14	PA	PA exergame with an avatar coach	Completion: 87.5%; teens enjoyed the game (mean enjoyment score 68%) Vigorous PA during 74.9% of the game
Duncan-Carnesciali et al [38], 2018	Location: United States N=198 Design: cross-sectional, survey-based design using quantitative and qualitative paradigms	Female: 97.5	Range 26-76	Diabetes	Avatar for diabetes management	Ethnicity including Arab or Middle Eastern, Asian, and White or European descents as well as age were significantly associated with an excellent rating of the video with P<.05
Klaassen et al [42], 2018	Location: N/A N=21 Design: usability study	Female: 52	Mean 13.9	Diabetes	Conversational coach game with feedback Integrates BCTs including information on consequences	Usability index of 44.18 (SD 21.18; low)
Sinoo et al [56], 2018	Location: Netherlands N=21 Design: experimental study	Female: 37	Mean 9.2 (SD 1.1)	Diabetes self-management	Avatar for gameplay and diabetes self-management vs robot	Preference for the robot (mean friendship score 4.0, SD 0.6) over the avatar (mean friendship score 2.9, SD 0.7) as a companion Usability moderate: 58.7 (SD 24.5) Similarity of avatar to robot led to greater friendship (P<.01)
Tongpeth et al [62], 2018	Location: Australia N=22 (development of the application) N=10 (feasibility testing) Design: pilot feasibility	Female: 10	Mean 52.2 (SD 10.4)	Cardiovascular: acute coronary syndrome management	An interactive, avatar-based education application for improving patients’ knowledge of, and response to, acute coronary syndrome symptoms	Symptom recognition increased: 24% Satisfaction: 87.3% Knowledge increase: 15.7%
Friedrichs et al [63], 2014	Location: Netherlands N=958 Design: 3-arm RCT	Female: 60.4	Mean 42.9 (SD 14.5)	PA; Dutch Short questionnaire	Avatar with a web intervention or a digital web-based text condition versus control	Significant increases in PA in the intervention arms versus control with B=0.39 in the avatar arm and B=0.44 in the text arms (P<.05) No differences between the text arm or the avatar arm for PA
Stein et al [25], 2017	Location: United States N=70 Design: longitudinal observational study	Female: 74.5	Mean 47 (SD 1.8); range 18-76	Weight and dietary intake	Lark Weight Loss Health Coach (participants were a part of a diabetes prevention weight loss program) Advice on dietary intake and PA BCTs used include motivation, encouragement, reminders, and education	31% increase in healthy eating Mean weight change: −2.4 kg (SE 0.82; 95% CI −4.03 to −0.77)
Thompson [66], 2016	Location: United States N=48 (round 1) N=43 (round 2) Design: mixed methods survey with qualitative interviews	Female: 50	Range 12-14	Preferences for a PA intervention	Exergame with a self-representation avatar	Desired gameplay with the avatar that could be controlled by eliciting the desired action: 62.5% male and 58.3% female Personalized avatar: 41.7% Most common avatar features to be customized: Body: 95.8% Clothing: 93.8% Hair color: 87.5%
Behm-Morawitz et al [33], 2016	Location: United States N=90, female=100% (the 2 male participants were excluded) Design: qualitative research and RCT	Female: 100	Range 18-61	Weight and PA self-efficacy	Avatar (embodied) and video game to promote PA	Findings support the use of the avatar for weight management t₁₈=2.15 (P<.05) with the intervention losing 1.75 lbs versus 0.91 lbs in the control No effects on dietary self-efficacy Strong correlation with avatar sense of self-presence and confidence in meeting health goals (r=0.95; P<.01) Themes: avatar benefits include motivation and assisting with self-efficacy for PA Barrier: games are not for everyone
Kuo et al [45], 2016	Location: Taiwan N=76 Design: 2-arm intervention in laboratory	Female: 63.15	Mean 21.2	Eating behavior observed in laboratory	Avatar that embodied the participants or was a weight-reduced (thinner) version of them	Avatars that embodied a thinner version of the participants shaped eating behaviors more compared with identical self-avatars; including selecting less ice cream (Cohen d=0.35; F1,73=7.8; P<.01) and opted for sugar free drinks (Cohen d=0.29; F1,73=6.0; P<.01)
Ruiz et al [54], 2016	Location: United States N=41 Design: laboratory study	Female: 0	Mean 64 (SD 7)	Cardiovascular behavioral risk factors (diet and exercise)	Avatar vs a voice (nonanimated) for behavior change linked with CVD	Avatar increased intentions (+1.56 points) to improve lifestyle behaviors relative to controls (Cohen d=0.77 P<.01; t₃₆=2.48) Differences in confidence to change risk of heart disease was nonsignificant
LeRouge et al [14], 2015	Location: United States N=41 Design: user-centered design, 3 phases with focus group and interviews	N/A	Teenagers: 12-17	Perceptions of the avatar for diet and exercise	Interactive avatar coach	Desire for a fun human-like interaction Desire for a lifestyle coach and personal embodiment avatar and an authoritarian one Desire for customization of the avatar Advice on activity on the go and meals when eating at home Goal setting Technical issues could be a barrier including the internet
Thomas et al [28], 2015	Location: United States N=37 Design: feasibility and usability study with pre-post test	Female: 100	Mean 55.0 (SD 8.2)	Weight-related eating behaviors	Conversational coach for weight (focuses on dietary intake and managing eating behaviors)	The coach assisted with perceptions of increased self-control over eating (confidence to control eating: +1 point (SD 0.2; P<.01) and skills for controlling eating +0.7 points (SD 0.1; P<.01)
Ruiz et al [53], 2014	Location: United States N=150 Design: RCT	Male: 100	Mean 62 (SD 7.9)	Diabetes (knowledge)	Computer program with an avatar to increase diabetes knowledge and medication (adherence)	There were no significant differences between the intervention group and control group in terms of knowledge, with P=.95 Satisfaction levels were higher in the digital intervention group (F4=3.11; P<.01)
Li et al [46], 2014	Location: Singapore N=140 Design: factorial design experiment	Female: 41	Range 9-12	PA attitudes, motivation, and game performance	Assigned to varying avatars (normal and overweight)	Healthy weight avatars linked with greater scores in motivation for Nintendo exercise (F1,134=5.49; P<.05 [boys]) attitude, and performance (F1,134=2.27; P<.05 [girls])
Napolitano et al [22], 2013	Location: United States N=128 (phase I) N=8 (phase 2) Design: mixed methods (pilot usability testing) study with interviews	Female: 100	Mean 34.1 (SD 13.0); range 18-60 (phase 1)	Weight, PA [14], and weight self-efficacy; satisfaction; preferences survey and interviews	Avatar for diet and exercise Informed by social cognitive theory Behavioral modeling Targeted self-efficacy 4 weeks	The avatar helpful: 87.5% Mean weight loss after 4 weeks: 1.6 (SD 1.7) kg All women found that it helped with their diet and exercise Most were interested in the avatar
Bickmore et al [34], 2013	Location: United States N=122 Design: 4-arm RCT (2 months)	Female: 61	Mean 33.0 (SD 12.6); range 21-69	Diet (NIH^t/NCI^u fruit and vegetable scan) and PA (IPAQ)	Animated counselor for diet and PA (separate and combined)	No significant differences between groups in PA after adjustment Fruit and vegetable servings significantly increased in the diet arm (F3,103=4.52; P<.01) No significant differences in weight or PA between groups Likability: Karen was perceived as nice by 35% of the participants 50% of the participants found Karen helpful
Johnoson-Glenberg et al [41], 2013	Location: United States N=19 Design: pilot feasibility study (pre-post study)	N/A	Grades 4-12 (ages 9-18)	Diet (nutrition and food choice test and knowledge)	Diet and exercise game (exergame) with an alien interactive coach	Differences in dietary knowledge of nutrition pre and post intervention (t=4.13; P<.01) and knowledge of the My Plate content in the study (t=3.29; P<.01)
Ruiz et al [52], 2012	Location: United States N=30 Design: comparative pilot with three arms (with randomization) intervention	N/A	N/A	PA	3D avatar-based VR intervention	Participants completing a 3D VR intervention mediated by avatars resembling the participants showed significant improvement in PA (P<.05) No significant effects of the intervention on obese or overweight participants
Mestre et al [47], 2011	Location: France N=6 Design: laboratory experimental study	N/A	Range 19-25	PA enjoyment	Digital coach paced participants in a VR bicycling setting	The VR coach and VR cycling were associated with higher levels of PA enjoyment (F2,10=13.24; P<.001) in the feedback group

^aRCT: randomized controlled trial.

^bBP: blood pressure.

^cGP: general practitioner.

^dPA: physical activity.

^eVR: virtual reality.

^fAI: artificial intelligence.

^gBCT: behavior change technique.

^hT2D: type 2 diabetes.

ⁱHbA_1c: hemoglobin A_1c.

^jFBG: fasting blood glucose.

^kPPBG: postprandial blood glucose.

^lHR: heart rate.

^mRR: respiratory rate.

ⁿCVD: cardiovascular disease.

^oSRHI: Self-Report Habit Index.

^pN/A: not applicable.

^qIPAQ: International Physical Activity Questionnaire.

^rPACES: physical activity enjoyment scale.

^sHAPA: Health Action Process Approach.

^tNIH: National Institutes of Health.

^uNCI: National Cancer Institute.