Lifestyle Intervention for Obesity and Eating Disorder Prevention in Transgender Adolescents

Quality of life will be measured using the World Health Organization Quality of Life - BREF (WHOQOL-BREF) questionnaire. The WHOQOL-BREF consists of 26 items covering four domains (physical health, psychological health, social relationships, and environment). Domain scores are transformed to a scale ranging from 0 to 100, with higher scores indicating better quality of life.

Body fat will be measured by dual-energy X-ray absorptiometry (DEXA).

Muscle mass will be measured by dual-energy X-ray absorptiometry (DEXA).

Bone density will be measured by dual-energy X-ray absorptiometry (DEXA).

BMI Z-score will be assessed by weight (kg) and height (m) that will be combined to report BMI in kg/m^2 Z-score according to the World Health Organization growth curves.

Food consumption will be assessed by three 24h food records.

Food insecurity will be assessed using the Brazilian Food Insecurity Scale (EBIA), a 14-item questionnaire assessing household access to food in the previous 90 days. The total score ranges from 0 to 14, with higher scores indicating greater food insecurity.

Diet quality will be assessed using the Diet Quality Scale (ESQUADA - Escala de Qualidade da Dieta), a questionnaire based on the Brazilian Dietary Guidelines. The total score ranges from 0 to 100, with higher scores indicating better diet quality.

Diet quality will also be assessed using the Healthy Eating Index-2020 (HEI-2020), a measure of adherence to the Dietary Guidelines for Americans. The total score ranges from 0 to 100, with higher scores indicating better diet quality.

Determinants of food choice will be assessed using the Eating Motivation Survey - Brief Version (TEMS), a questionnaire assessing motivations underlying food choices across multiple domains. Items are rated on a 5-point Likert scale ranging from 1 to 5, with higher scores indicating stronger endorsement of the respective eating motivation.

Screening for eating disorders will be conducted using the SCOFF questionnaire, a 5-item screening tool with yes/no responses. Scores range from 0 to 5, with higher scores indicating greater likelihood of an eating disorder. A score of 2 or more positive responses suggests a possible eating disorder and indicates the need for further assessment.

Eating disorder symptoms will be assessed using the Eating Disorder Examination Questionnaire (EDE-Q), a 28-item self-report instrument assessing eating disorder psychopathology over the previous 28 days. Items are rated on a 7-point scale ranging from 0 to 6, with higher scores indicating greater eating disorder psychopathology. The global score ranges from 0 to 6, representing the mean of four subscale scores

Body dissatisfaction will be assessed using the Body Shape Questionnaire (BSQ), a 34-item questionnaire measuring concerns about body shape. Items are rated on a 6-point Likert scale, with total scores ranging from 34 to 204, where higher scores indicate greater body dissatisfaction.

Body image apprciation will be assessed using the Body Appreciation Scale-2 (BAS-2), a 10-item questionnaire evaluating body appreciation and respect for one's body. Items are rated on a 5-point Likert scale, with total scores ranging from 10 to 50, where higher scores indicate greater body appreciation.

Physical activity and sedentary behavior will be assessed using the Physical Activity Questionnaire from the 2015 follow-up of the 1993 Pelotas Birth Cohort, which includes questions on leisure-time physical activity, active transportation, screen time, and sedentary behavior. Outcomes will be reported as time spent in physical activity and sedentary behaviors (minutes per week or hours per day), with higher physical activity indicating healthier behavior and higher sedentary time indicating less favorable behavior.

Participants' perceptions of the intervention will be assessed through post-intervention semi-structured focus groups. Audio-recorded discussions will be transcribed and analyzed using thematic qualitative analysis to identify key themes related to participants' experiences, perceived benefits, and challenges of the intervention.