Does Motivational Interviewing Improve Behavioral Weight Loss Outcomes for Obesity?

Weight was measured to the nearest 0.1 kg using a balance beam scale

Time frame: Mean weight recorded at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

The mean number of missed behavioural weight loss sessions (out of 24 sessions)

Time frame: Assessed once at the end of the behavioural weight loss program (week 12)

A measure of systolic and diastolic blood pressure was taken in a standardized manner according to the Canadian Hypertension Education Program Guidelines (Hemmelgarn et al., 2006). Three different readings of blood pressure were taken at each time point (baseline and 6 month follow up), and the average of the three readings was taken as the measure of blood pressure for each time point.

Time frame: Mean blood pressure 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

A measure of systolic and diastolic blood pressure was taken in a standardized manner according to the Canadian Hypertension Education Program Guidelines (Hemmelgarn et al., 2006). Three different readings of blood pressure were taken at each time point (baseline and end of behavioural weight loss program), and the average of the three readings was taken as the measure of blood pressure for each time point.

Time frame: Mean blood pressure at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

A digital scale (Tanita BWB-800S), which assessed weight to the nearest 0.1 kg, was used to assess weight for the 6 month follow up assessment, and the height measured at the beginning of the behavioural weight loss program was used to calculate BMI. BMI was calculated as weight in Kilograms divided by height in meter squared.

Time frame: Mean BMI 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Weight was measured to the nearest 0.1 kg using a balance beam scale, height was measured to the nearest 0.1 cm using a stadiometer at the beginning of the behavioural weight loss program. BMI was calculated as weight in Kilograms divided by height in meters squared.

Time frame: Mean BMI at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of confidence for change after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how confident they feel about succeeding with losing weight on a scale from 0 not confident to 10 was very confident. Thus lower scores reflect lower levels of confidence for change, and higher scores reflect higher levels of confidence for change. Their raw score from 0 to 10 on this measure was taken as their Confidence for Change rating score.

Time frame: Confidence for change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Self-report ratings of confidence for change after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how confident they feel about succeeding with losing weight on a scale from 0 not confident to 10 was very confident. Thus lower scores reflect lower levels of confidence for change, and higher scores reflect higher levels of confidence for change. Their raw score from 0 to 10 on this measure was taken as their Confidence for Change rating score.

Time frame: Confidence for change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Time frame: Mean dietary behaviour score as measured by the overall DHQ score, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Time frame: Mean dietary behaviour score as measured by the overall DHQ score, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Time frame: Mean dietary behaviour score as measured by the overall DHQ score, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Time frame: Mean eating disorder symptomology as measured by the global EDE-Q score, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Time frame: Mean eating disorder symptomology as measured by the global EDE-Q score, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Time frame: Mean eating disorder symptomology as measured by the global EDE-Q score, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of importance of change after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how important it is for them personally to lose weight on a scale from 0 not important to 10 was very important. Thus lower scores reflect lower levels of importance for change, and higher scores reflect higher levels of importance for change. Their raw score from 0 to 10 on this measure was taken as their Importance for Change rating score.

Time frame: Importance of change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of importance of change after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how important it is for them personally to lose weight on a scale from 0 not important to 10 was very important. Thus lower scores reflect lower levels of importance for change, and higher scores reflect higher levels of importance for change. Their raw score from 0 to 10 on this measure was taken as their Importance for Change rating score.

Time frame: Importance of change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Time frame: Mean physical activity as measured by the PPAQ, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Time frame: Mean physical activity as measured by the PPAQ, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Time frame: Mean physical activity as measured by the PPAQ, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of readiness for change after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how ready they are to lose weight on a scale from 0 not ready to 10 was very ready. Thus lower scores reflect lower levels of readiness for change, and higher scores reflect higher levels of readiness for change. Their raw score from 0 to 10 on this measure was taken as their Readiness for Change rating score.

Time frame: Readiness for change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Self-report ratings of readiness for change after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how ready they are to lose weight on a scale from 0 not ready to 10 was very ready. Thus lower scores reflect lower levels of readiness for change, and higher scores reflect higher levels of readiness for change. Their raw score from 0 to 10 on this measure was taken as their Readiness for Change rating score.

Time frame: Readiness for change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-efficacy for engaging in physical activity was measured by the Exercise Self-Efficacy questionnaire (ESE; Nigg & Riebe, 2002). Participants rate their confidence that they could exercise on a 5-point Likert scale for six barriers to exercise (e.g., bad weather, stress, availability of equipment). Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Time frame: Mean self-efficacy for engaging in physical activity measured immediately after the first MI or attention control interview (week 1 - 2)

Self-efficacy for engaging in physical activity was measured by the Exercise Self-Efficacy questionnaire (ESE; Nigg & Riebe, 2002). Participants rate their confidence that they could exercise on a 5-point Likert scale for six barriers to exercise (e.g., bad weather, stress, availability of equipment). Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Time frame: Mean self-efficacy for engaging in physical activity measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-efficacy related to eating patterns was measured by the Weight Efficacy Life-Style Questionnaire (WEL; Clark, Abrams, Niaura, Eaton, & Rossi, 1991). This self-report questionnaire yields five subscale scores, which rate self-efficacy for controlling eating in different situations/dimensions: negative emotions, availability, social pressure, physical discomfort, and positive activities. A global/total score (which ranges from 0 - 180) is obtained by summing the scores of each of the five subscales. Higher scores are indicative of greater self-efficacy (i.e., higher scores = better outcome).

Time frame: Mean self-efficacy related to eating patterns measured immediately after the first MI or attention control interview (week 1 to 2)

Self-efficacy related to eating patterns was measured by the Weight Efficacy Life-Style Questionnaire (WEL; Clark, Abrams, Niaura, Eaton, & Rossi, 1991). This self-report questionnaire yields five subscale scores, which rate self-efficacy for controlling eating in different situations/dimensions: negative emotions, availability, social pressure, physical discomfort, and positive activities. A global/total score (which ranges from 0 - 180) is obtained by summing the scores of each of the five subscales. Higher scores are indicative of greater self-efficacy (i.e., higher scores = better outcome).

Time frame: Mean self-efficacy related to eating patterns measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

a digital scale (Tanita BWB-800S), which assessed weight to the nearest 0.1 kg, was used for the 6 month follow-up assessment

Time frame: Mean weight 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.