Table 1 Main results of the included studies

Boff et al. [30]

(2018)

To evaluate the effectiveness of a TTM-based intervention on anthropometric, metabolic, and motivational outcomes in adolescents with obesity.

Sample:

65

Age:

15–18 y

Gender:

Male: 57%

Female: 43%

Country:

Brazil

Who delivered:

Nutritionists, psychologists, and other health professionals.

To whom:

Adolescents who were with overweight or obesity

Format:

Motivational Interdisciplinary Group (IG) and the Traditional Health Education Group (CG)

Context:

Online

Content:

For the IG, the sessions focused on motivation to change eating habits through the stages of change, the processes of behavioral change, and enhanced decision-making and self-efficacy. The CG received traditional education in health. The primary outcomes were changes in TTM variables and anthropometric measures.

Duration:

3 months

Follow-up: Baseline and after 12 weeks

Frequency:

12 weekly meetings for 1h30min

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main results:

There was a statistically significant difference only in decisional balance between groups over time. No significant differences for dietary intake were found.

Brick et al. [17, 18]

(2017)

To evaluate stage progression in a large computer-based, TTM- tailored intervention involving physical activity, fruit and vegetable consumption, TV viewing, and substance abuse prevention.

Sample:

2983

Age:

10–15 y

(mean 11.4 y)

Gender:

Male: 52.2%

Female: 47.8%

Country:

United States

Who delivered:

Research assistants

To whom:

Students

Format: Energy balance intervention and alternate intervention groups

Context:

The intervention was delivered in school computer laboratories using laptops provided by the study

Content:

The energy balance group received an intervention to increase fruit and vegetable consumption. The alternate group received an intervention to prevent/cessate smoking and alcohol use. Both groups received TTM-tailored intervention, and feedback

Duration:

3 years

Follow-up: Baseline, follow up assessment every year for 3 years

Frequency:

5 sessions

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

Regarding fruit and vegetable intake, the energy balance group had greater percentages of consumption than the substance use prevention group, progressing to the action or maintenance at 12, 24, and 36 months.

Di Noia et al. [19, 20]

(2008)

To examine the efficacy of a TTM-based computer-mediated intervention to increase fruit and vegetable consumption among economically disadvantaged African American adolescents.

Sample:

507

Age:

11–14 y

(mean 12.4 y)

Gender:

Male: 39%

Female: 61%

Country:

United States

Who delivered:

Research staff

To whom:

African American adolescents from Youth services agencies

Format:

Computer intervention (CIN) and Control

Context:

CD-ROM mediated intervention content in Youth services agencies

Content:

The intervention addressed the health benefits of consuming five or more daily servings of fruits and vegetables. The CIN received stage-tailored sessions

Duration:

4 weeks

Follow-up:

2 weeks before and after the intervention

Frequency:

4 onsite 30-min weekly sessions

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main Results:

The fruit and vegetable intake of those involved in the program increased about 38% more than the control group, an average increase of 0.9 daily servings of fruits and vegetables. More youths in the intervention than in the control group progressed to later stages.

Filgueiras et al. [31]

(2018)

A multidisciplinary TTM-based motivational intervention involving nutritional counseling for low-income adolescents with obesity.

Sample:

16

Age:

11–17 y

Gender:

Male: 57%

Female: 43%

Country:

Brazil

Who delivered:

Nutritionists and psychologists

To whom:

Adolescents with obesity

Format:

Individual nutritional counseling and nutritional education workshops

Context:

The nutritional education workshops were conducted in the Center of Nutritional Recovery and Education (CREN)

Content:

All participants went through individual nutritional counseling, according to their stage, in a CREN office, to help them overcome the difficulties and barriers involved in changing dietary habits, reinforcing the positive aspects of the changes that had already been made.

Duration:

13 months

Follow-up: Baseline, 6 and 13 months

Frequency:

Once a week

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

At the beginning, about 70% of the participants were in the precontemplation stage. After six months, 60% had changed to the action stage. At the end of the intervention, all participants had reached the action or maintenance stages.

Freen et al. [21]

(2005)

To examine the effectiveness of 8 sessions of a TTM/Health promotion intervention

(Internet/video-based) to increase physical activity and reduce dietary fat among 7th graders.

Sample:

103

Age:

12–14 y

Gender:

Male: 40.6% Female: 59.4%

Country:

United States

Who delivered:

Research staff

To whom:

Students

Format:

Control group and Intervention group

Context:

The intervention was conducted in a computer laboratory where each student had a computer

Content:

The focus of the intervention was on reducing dietary fat with strategies appropriate for all stages of change, particularly for those in precontemplation and contemplation stages

Duration:

1 month

Follow-up:

1 week before and after intervention

Frequency:

8 sessions of 40 min (1 class period)

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Main Results:

Among those who participated in more than half the sessions, dietary fat decreased from 30.7 to 29.9% of the total calorie intake. The diet of those who participated in less than half of the sessions was not significantly different than the control group.

Freen et al. [22]

(2003)

A stage-based intervention to reduce fat consumption in middle school students.

Sample:

74

Age:

12–17 y

(mean 13.82 y)

Gender:

Male: 47%

Female: 52%

Country:

United States

Who delivered:

Graduate nursing students in pediatric nursing

To whom:

Students

Format:

Control group and Stages of change intervention group

Context:

All classroom interventions took place during the Family and Consumer Education class

Content:

Classroom interventions incorporated processes appropriate for the precontemplation and contemplation stages of change by using multiple instructional methods appropriate to middle school students, content to increase knowledge, and peer modeling of skills

Duration:

4 class periods

Follow-up:

Pre-test,and post-test

Frequency:

4 sessions of 45 min

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main Results:

The average percentage of fat in dietary intake ranged from 30.7 to 32.8%; the percentage of fat increased less in the intervention group than the control group.

Gur et al. [32]

(2019)

To evaluate the impact of a Transtheoretical Model-based programme titled ‘Fruit & Vegetable-Friendly’ on the fruit and vegetable (F&V) consumption of adolescents.

Sample:

702

Age:

9–15 y

(mean 12.02 y)

Gender:

Male: 45.2%

Female: 54.8%

Country:

Turkey

Who delivered:

Research team

To whom:

Students and their families

Format:

Single group

Context:

The intervention took place in the classroom

Content:

The intervention presented different components in order to address every stage.

Duration:

8 weeks

Follow-up: Baseline, post-intervention, and 6 months after the intervention.

Frequency:

Not reported

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main Results:

The difference in consumption of fruit and vegetable six months after the intervention was 3·7 portions/d for those who were in the precontemplation stage, 3·0 portions/d in those in the contemplation stage and 2·4 portions/d in those in the preparation stage. The difference for those in the action stage was 0·8 portions/d. In the maintenance stage, total F&V consumption had decreased by 1·2 portions/d. Students in the action and maintenance stages increased, while the percentage of students in the precontemplation, contemplation and preparation stages decreased.

Haerens et al. [23]

(2007)

To examine the mediating effects of changes in psychosocial determinants of dietary fat intake on changes in fat intake in adolescent girls.

Sample:

788

Age:

11–15 y

(mean 12.9 y)

Gender:

Female: 100%

Country: Belgium

Who delivered:

School staff

To whom:

Female students

Format:

Intervention and Control groups

Context:

The intervention occurred during class hours

Content:

The students completed a youth-based version of the computer-tailored fat intake intervention. The TTM was used to define the content and approach of feedback.

Duration:

1 h

Follow-up:

Baseline and 1 year after intervention

Frequency:

1 class hour

Outcome analyzed: Dietary intake

TTM constructs used:

Self-efficacy

Decisional balance

Main Results:

On average, fat intake in the intervention group was reduced by 9.0 g/day vs. the control group.

Jalambadani et al. [24]

(2017)

To investigate the effects of education (TTM) on reducing fast food consumption among female adolescents suffering from obesity and overweight in Sabzevar, Iran.

Sample:

420

Age:

15–18 y

(mean 16.36 y)

Gender:

Female: 100%

Country:

Iran

Who delivered:

Research staff

To whom:

Female students with obesity

Format:

Education and Control groups

Context: The intervention took place in the classroom

Content:

The education group participated in meetings that focused on nutrition concepts and identified methods to stay motivated. The meetings also included discussion with students on difficulty and ease in consumption reduction of fast food.

Duration:

12 weeks

Follow-up:

Pre-test, and post-test

Frequency:

60 min, twice a week

Outcome analyzed: Dietary intake and nutritional knowledge

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main Results: The average rates of stages of change, processes of change, and self-efficacy in the education group improved significantly. No statistical significance was obtained for decisional balance between the two groups after the intervention. No significant differences for dietary intake were found.

Lana et al. [25]

(2013)

To assess the impact of a web-based intervention supplemented with text messages to reduce cancer risk linked with smoking, unhealthy diet, alcohol consumption, obesity, sedentary lifestyle and sun exposure.

Sample:

737

Age:

12–16 y

Gender:

Male: 45.2%

Female: 54.8%

Country:

Spain and Mexico

Who delivered:

Self-delivered

To whom:

Students

Format:

Experimental group 1 (EG1), Experimental group 2 (EG2), and Control group

Context:

Online

Content:

The EG1 and EG2 members had free access to a tailor-made and interactive website. During the academic year, this website was periodically updated with different school and leisure activities related to the avoidance of risk behaviors. The EG2 also received encouraging text messages. Cancer risk behaviors, such as not eating enough fruits and vegetables and being overweight were assessed before and after the study.

Duration:

9 months

Follow-up:

Baseline and post-test

Frequency:

9 months of website access

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

Both groups decreased by more than 70% the number of students who did not consume enough fruit.

Mauriello et al.

[26, 27]

(2010)

To report on the effectiveness of Health in Motion, a computer tailored multiple behavior intervention for adolescents.

Sample:

1800

Age:

Mean 15.9 y

Gender:

Male: 49.2%

Female: 50.8%

Country: England

Who delivered:

Research assistants

To whom:

Students

Format:

Multimedia intervention and Control groups

Context:

All sessions were administered via computers in school computer laboratories

Content:

Students self-directed through the 30-min program in which they completed a series of TTM-based assessments and received stage-matched and tailored feedback messages related to fruit and vegetable consumption based on their responses.

Duration:

2 months

Follow-up:

Baseline and after 6 and 12 months

Frequency:

3 sessions

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

The multimedia intervention group reported eating significantly more servings of fruits and vegetables than the control group at 2 months, 6 months, and 12 months.

Individuals within the intervention group were found 1.4–4.2 times more likely to progress to action or maintenance.

Muzaffar et al. [33]

(2019)

To evaluate the afterschool PAWS (Peer-education About Weight Steadiness) Club program delivered by peer or adult educators to improve food choices, physical activity, and psychosocial variables related to healthy eating.

Sample:

109

Age:

11-14y

Gender:

Male: 30%

Female: 70%

Country:

United States

Who delivered:

Educators

To whom:

Students

Format:

Peer-led and adult-led groups

Context:

The intervention occurred at school

Content:

The curriculum was focused on building healthy eating patterns and addressing stages of change variables. Printed goal-setting worksheets were provided to the participants at each of the 12 sessions.

Duration:

12 weeks

Follow-up: Baseline, post-intervention, and 6 months after the intervention

Frequency:

Weekly sessions of 1h30min

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

All participants significantly reduced kcals/day from baseline to 6-months post-intervention. For the peer-led group, self-reported intake of whole grains (servings/day) increased from baseline to 6-months post-intervention.

Toral et al. [28]

(2012)

To assess the impact of a six-month stage-based intervention on fruit and vegetable intake for perceived benefits, barriers, and self-efficacy among adolescents.

Sample:

771 Age:

11–19 y

Gender:

Male: 40.5% Female: 59.5%

Country:

Brazil

Who delivered:

Research staff

To whom:

Students

Format:

Intervention Group and Control Group

Context:

The materials were distributed in classrooms and by mail

Content:

The students received printed educational materials for promoting healthy dietary habits, both in classrooms and by mail. The materials were directed toward the participants’ stages of change.

Duration:

6 months

Follow-up: Baseline, and follow-up assessment after the intervention

Frequency:

6 monthly newsletters and magazines

Outcome analyzed: Dietary intake

TTM constructs used:

Processes of change

Stages of change

Decisional balance

Self-efficacy

Main Results:

No significant changes were found in fruit and vegetable intake, benefits, barriers, or perceived self-efficacy.

Yusop et al. [29]

(2018)

To assess the effectiveness of a stage-based lifestyle modification intervention for children with obesity.

Sample:

40

Age:

7–11 y

(mean 9.8 y)

Gender:

Male: 52.5%

Female: 47.5%

Country: Malaysia

Who delivered:

Dietitians and physical education professionals

To whom:

Students with obesity and parents

Format:

Intervention group and Control group

Context:

The intervention study was conducted at an university Dietetic Clinic

Content:

Intervention group received stage-based lifestyle modification intervention based on the Nutrition Practice Guideline for the Management of Childhood Obesity, while control group received standard treatment.

Duration:

24 weeks

Follow-up: Baseline, follow up every month and at the end of the intervention

Frequency:

3 sessions of 2 h of aerobic exercise on weekends (once every 2 months); 1 h of Nutritional counseling every week.

Outcome analyzed: Dietary intake

TTM constructs used:

Stages of change

Main Results:

Dietary intake was not significantly different between the two groups.