Does Motivational Interviewing Improve Behavioral Weight Loss Outcomes for Obesity? (BWLP+MI)

Adding Motivational Interviewing to a Behavioral Weight Loss Treatment for Obesity: A Randomized Controlled Trial

The purpose of this study is to determine whether adding motivational interviewing (MI) to a behavioural weight loss program (BWLP) results in improved weight loss for adults who are overweight or obese.

Although behavioural weight loss programs (BWLP) are typically the first line of treatment for obesity, they are often plagued by high attrition rates and poor adherence. Studies evaluating the benefit of adding motivational interviewing (MI) to BWLPs have yielded mixed findings. The main purpose of this randomized controlled trial was to assess the efficacy of adding MI to a BWLP on weight loss and adherence outcomes among 135 overweight and obese individuals enrolled in a 12-week (24 session) BWLP. This study used a randomized, controlled, longitudinal, between-subjects design to investigate the effects of a two-session MI intervention on weight loss in participants enrolled in a BWLP. Patients received either two 45-60 minute MI interventions or two 45-60 minute attention control interviews. The control group interview consisted of questions ascertaining weight history, diet history, dietary awareness and physical activity. Questions for the control group focused primarily on assessment of past behaviour whereas questions for the MI group focused on enhancing motivation by exploring and resolving ambivalence. Weight was measured at baseline, end of the BWLP, and 6 months following BWLP completion. Program adherence (measured as number of BWLP sessions attended out of 24) was assessed as a secondary dependent measure. Importance, readiness, and confidence for weight change were assessed at baseline and then immediately following each interview (either MI or control). In addition, several other secondary outcome measures were assessed at baseline, end of the BWLP, 1 month follow-up, and 6 month follow-up. Research personnel informed all BWLP participants about the study at the initial BWLP group intake assessments, which occurred just prior to the commencement of the formal BWLP. Individuals who expressed interest in participating were contacted by phone by a research assistant and screened for eligibility. If eligible, an appointment was made for the first MI/control session which was scheduled within the first two weeks of the BWLP. Randomization occurred immediately prior to this interview. Participants were then contacted during the 10th week of the BWLP to schedule a second MI/control session, which occurred approximately during the 12th week of the program. Participants were all contacted several weeks following program completion to schedule the one-month follow-up assessment. Finally, all participants were contacted approximately five months following program completion in order to schedule the six-month follow-up assessment. Sessions were tape recorded for all participants for quality assurance purposes. A subset of tapes were used to assess for treatment integrity.

Two 45-60 minute motivational interviewing sessions focusing on exploring and resolving ambivalence towards change.

Two 45-60 minute semi-structured interviews, acting as a pseudo-intervention, ascertaining information relevant to health history, weight history, diet history, as well as dietary and physical activity habits.

The semi-structured MI protocol was a 45-60 minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.

The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).

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

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.

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.

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.

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

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.

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

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.

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

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).

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

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).

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

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).

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

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.

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.

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).

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

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).

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

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).

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

Self-efficacy Related to Eating Patterns After the First Motivational Interviewing or Attention Control Interview, Week 1 - 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).

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

Self-efficacy for Engaging in Physical Activity After the First Motivational Interviewing 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).

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

Self-efficacy Related to Eating Patterns After the Second Motivational Interviewing or Attention Control Interview, Week 12

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).

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

Self-efficacy for Engaging in Physical Activity After the Second Motivational Interviewing or Attention Control Interview, Week 12

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).

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

Importance of Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1 - 2

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.

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

Readiness for Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1 -2

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.

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

Confidence for Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1- 2

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.

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

Importance for Change Ratings After the Second Motivational Interview or Attention Control Interview, Week 12

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.

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

Readiness for Change Ratings After the Second Motivational Interviewing or Attention Control Interview, Week 12

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.

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

Confidence for Change Ratings After the Second Motivational Interviewing or Attention Control Interview, Week 12

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.

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

Inclusion Criteria: Overweight to obese (BMI greater than or equal to 25 kilograms per meter squared). Exclusion Criteria: Pregnancy (or intention of becoming pregnant within 9 months) Health issues that would preclude participation in physical activity Concurrent involvement in another weight loss program.

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