Table 3 Research outcomes and internal consistencies

 State body satisfaction

A single 11-point scale assessing the immediate impact of a chatbot technique on participants’ state body satisfaction (How satisfied are you with your appearance, right now, in this moment?).

Total score range 0 (not at all) to 10 (very much). Higher scores reflect greater satisfaction.

Start of chatbot experience.

Post-intervention technique.

12-, 16-, 23.5-h after non-engagement.

 Trait body satisfaction

Body Esteem Scale for Adolescents & Adults in Brazil [46, 47].

Appearance Positive (AP; e.g., I like how I look like in photos), Appearance Negative (AN; e.g., I feel ashamed about my appearance) and Weight (e.g., I am satisfied with my weight).

Mean subscale scores range between 0 (never) and 5 (always). Higher scores reflect higher esteem. Internal consistency: AP = .85; AN = .88; Weight = .89.

T1- T4

 State affect

A single 11-point scale assessing the immediate impact of a chatbot technique on participants’ state affect (How happy are you, right now, in this moment?).

Total score range between 0 (not at all) to 10 (very much). Higher scores reflect greater positive affect.

Start of chatbot experience.

Post intervention technique.

12-, 16-, 23.5-h after non-engagement.

 Trait affect

The Positive and Negative Affect Scale for Children 8-item; PANAS-C8 [48]

8-items related to emotive states (4 positive [e.g., joyful]; 4 negative [e.g., irritated]).

Positive and negative affect subscale scores range between 1 (not at all) and 5 (extremely). Higher scores reflect greater positive or negative affect. Internal consistency: PA = .77; NA = .76

T1 - T4

 Trait body image self- efficacy

A purpose-built measure, The Body Image Self-Efficacy Scale, derived from existing self-efficacy measures [49,50,51].

5 visual analogue scales (VAS; 0 [not at all confident] to 100 [very confident]) assessing participants’ belief in their ability to execute strategies to improve their body image (e.g., I am able to learn and practice new skills to help improve my body image).

Total mean scores range between 0 and 100. Higher scores reflect greater body image self-efficacy. Internal consistency: .82

T1 - T4

 Intervention adherence

Digital metrics will assess participants engagement with the chatbot, including:

• Percentage of participants who complete the intervention (e.g., minimum of 1 technique completed over the 72-h intervention period);

• Percentage of participants who enter the intervention but do not complete the intervention;

• Percentage of participants who complete each intervention technique;

• Average number of techniques completed;

• Average length of time taken to complete each technique;

• Average length of time spent engaging with the chatbot over the 72-h period.

72-Hour Intervention Period

 Intervention acceptability

11 items assessed participants acceptability of the chatbot. Factors included:

• Emotive response to the chatbot (e.g., enjoyment, interest, comfortability);

• Relevance (e.g., pertinence, importance and helpfulness of the content to the user and other young people in Brazil);

• Ease of use (e.g., speed and accuracy of responses); and

• Willingness to recommend (e.g., how likely the user would recommend Topity to a friend and re-engage in the future).

Item scores range between 1 (e.g., not at all enjoyable) and 7 (e.g., very enjoyable). Higher scores reflect greater acceptability.

T4