Abstract
Background
The purpose of this study was to evaluate whether effectiveness of a special intervention (SI) to improve diet versus a control intervention (CI) differs by readiness to reduce dietary saturated fat based on the Transtheoretical Model stages of change among family members of hospitalized CVD patients.
Methods
Stage of change (precontemplation, contemplation, preparation, action, maintenance) was assessed by standardized questionnaire. Diet was measured by Block 98 Food Frequency Questionnaire at baseline and one-year in participants in the Family Intervention Trial for Heart Health (n=501; 36% racial/ethnic minorities; 66% female). Therapeutic Lifestyle Change diet education was provided to each SI subject tailored to baseline stage of change. Multivariable linear regression was used to examine whether the effect of the intervention was modified by stage of change.
Results
Baseline saturated fat and cholesterol intakes were lower among those in maintenance stage vs. others [(9.9% vs. 11.2% kcals; p<.0001) and (112.2 vs. 129.7 mg/1000kcal; p=.0003) respectively]. Overall, change in the percentage of calories from saturated fat from baseline to one-year was −0.7 in the SI vs. −0.4 in the CI (p=.18). Among participants in contemplation greater reductions in saturated fat (−2.1% vs. +0.3% kcals; p=.04) and cholesterol (−34.0 vs. +32.6 mg/1000kcal; p=.01) were seen in the SI vs. CI. The SI was more likely than CI to achieve new adherence to a diet <10% saturated fat /<300mg cholesterol at one-year among those not in maintenance stage (30% vs. 15%; p=.03). CI participants were more likely than SI to revert to lower levels on the stage of change continuum from baseline to one-year (17% vs. 7%; p=.002).
Conclusion
Effectiveness of an intervention to lower saturated fat varies by baseline stage of change among family members of hospitalized CVD patients. This may be important to consider when designing research or clinical diet interventions.
INTRODUCTION
Adherence to a heart healthy diet pattern promotes improved risk factor levels such as lower total blood cholesterol and lower blood pressure and reduces cardiovascular disease (CVD) risk (1). However, the effectiveness of educational interventions to promote positive diet changes may differ based on participant readiness to change behavior. Risk factor intervention programs designed to promote lifestyle change have increasingly incorporated psychological models of behavior change and behavioral stage theories, such as the Transtheoretical Model stages of change (2, 3). Such models are built on the premise that behavior change will occur as an individual passes through a series of qualitatively different stages and that barriers to behavior change (e.g. diet change) will differ by the stage a person is in (2). It has been suggested that interventions tailored to a person’s stage of change may be more effective to promote desired behavior changes compared to traditional intervention approaches (2).
The National Heart Lung and Blood Institute sponsored Family Intervention Trial for Heart Health (FIT Heart) tested the effectiveness of a screening and educational intervention for family members of patients hospitalized with CVD. It demonstrated effectiveness of the program to improve CVD lifestyle factors, such as diet, in CVD patient family members one year later (4). The diet education component of the FIT Heart special intervention was developed using the Transtheoretical Model of behavior change.
The Transtheoretical Model of behavior change is widely used and has been applied to several behaviors including smoking, physical activity and diet (2). It is based on the premise that behavior change is a dynamic process that involves progression across stages: 1) precontemplation (not considering behavior change), 2) contemplation (thinking about behavior change), 3) preparation (making plans to change behavior), 4) action (changing behavior), and 5) maintenance (continuing new behavior) (3).
Different intervention approaches were provided to participants based on their stage of readiness to reduce saturated fat in their diet. For example, participants in precontemplation received more information about saturated fat reduction in connection with CVD risk reduction. In contrast, participants in the maintenance stage of change were provided with social and environmental support strategies and problem-solving skills (5). Motivational interviewing, a client-centered style of counseling that seeks to create a positive interpersonal atmosphere and enhance motivation to change by exploring and resolving ambivalence, was utilized during in-person study visits and telephone follow-up calls (6).
Few randomized controlled trials have evaluated the impact of educational interventions on promoting desirable diet change among family members of CVD patients (7–14). Effective lifestyle interventions for family members of CVD patients are important to develop, because family members may be at increased risk of CVD themselves due to shared genes and/or lifestyle habits with the CVD patient (1). The purpose of this study was to evaluate the effectiveness of a stage of change-based diet intervention that incorporated motivational interviewing-type counseling on the intake of saturated fat, and other key nutrients, among family members of hospitalized CVD patients.
METHODS
FIT Heart was a year-long single-site randomized controlled trial. It evaluated a special intervention (SI) with personalized risk factor screening, National Cholesterol Education Program Adult Treatment Panel (ATP) III Therapeutic Lifestyle Changes (TLC) counseling (1), and progress reports to physicians versus a control intervention (CI) on clinical and lifestyle risk factors for CVD. Recruitment of participants took place between January 2005 and June 2007. Details of the study design, recruitment and flow have been previously published and follow-up at one-year was 94% (4). The 501 participants were English and Spanish speaking family members of cardiac patients admitted to New York-Presbyterian Hospital. Mean age was 48 years, 66% were female, 36% were racial/ethnic minorities, and participants had an average saturated fat intake of 10.7% of daily calories at baseline. A family member was defined as a 1) blood relative or 2) spouse or other individual (e.g. adopted son/daughter) living with the index case or who has cohabitated with him/her for a minimum of one year within the previous five, or for ten or more years in the past.
Exclusion criteria included established CVD, diabetes, active liver disease, chronic kidney disease, life expectancy fewer than five years, current or planned pregnancy, prescription of a diet non-compatible with TLC diet recommendations (1), or participation in a clinical study within three months of randomization. All subjects meeting inclusion criteria completed informed consent and HIPAA procedures prior to study participation. The study was approved by the Institutional Review Board of Columbia University Medical Center.
Randomization was completed using a web based application with a MySQL AB database system (version 12.22, 2002, Sun Microsystems, Inc., Santa Clara, CA) that generated group assignment after enrollment at the baseline visit. Randomization was blocked based on gender and race/ethnicity. Participants were randomized to receive either the SI or the CI.
Measurements
Diet Assessment
Participant diet was assessed in person by trained interviewer-assisted questionnaire at baseline and one-year using the Block 98 Food Frequency Questionnaire (FFQ). Five interviewers were trained to administer the Block 98 FFQ by the Bionutrition Research Core of the Irving Center for Clinical and Translational Research at Columbia University. A registered dietitian oversaw quality assurance throughout the course of the study. The Block 98 FFQ has been extensively studied and validated (15–20). The questionnaire takes 30–40 minutes to administer and records the frequency and portions of foods consumed (21). Completed questionnaires were scanned and analyzed by NutritionQuest (Berkeley, CA).
Saturated fat (g), dietary cholesterol (mg), monounsaturated fat (g), polyunsaturated fat (g), trans fat (g), fruit and vegetable (servings), and caloric intake were extracted from the Block 98 FFQ. Percent of calories from saturated fat, monounsaturated fat, polyunsaturated fat, and trans fat was calculated using the equation: [(grams fat/day)(9 calories/gram)]/(calories/day). Adherence to Step I diet was defined as <10% of calories from saturated fat and <300mg dietary cholesterol per day. Adherence to a TLC diet was defined as <7% of calories from saturated fat and <200mg dietary cholesterol per day (1).
In addition, participants were screened at baseline and one-year using the MEDFICTS questionnaire, an instrument included in the ATP III guidelines (1, 22). MEDFICTS provides a brief method to record food intake, portion size, and frequency of intake. It focuses on primary contributors of total fat, saturated fat, and cholesterol in the diet (i.e., Meats, Eggs, Dairy, Fried foods, fat In baked goods, Convenience foods, fats added at the Table and Snacks) with immediate results (23). The questionnaire yields a continuous score correlated with dietary saturated fat and cholesterol intake (22–24).
Risk Factor Measurements
Demographics, medical and family history, education level, and other characteristics were obtained at baseline and one-year by questionnaire. Age group was defined as having age as a CVD risk factor (≥45 years in men and ≥55 years in women versus <45 years in men and <55 years in women). Race/ethnicity was defined as non-white versus white. Education level was defined as less than or equal to high school education versus greater than high school education. Study forms were available in English and Spanish and research staff was bilingual English/Spanish speaking.
Study personnel were trained to use standardized methods for anthropometric measurements to minimize the risk of measurement error differential by examiner (25). Overweight/obese status was defined at body mass index (BMI) ≥25 (26). Measurements were conducted at baseline and one-year with one-year measurements completed by examiners blinded to group assignment.
Stage of Change
Each participant’s stage of change was assessed at baseline and one-year by standardized questionnaire adapted from previous work conducted in the area of diet and stage of change and documented in his/her chart (5). A description of the stage of change assessment criteria is presented in Table 1. Briefly, stage of change was assessed by ascertaining whether a participant was currently following a reduced saturated fat diet and, if so, for how long. A definition of saturated fat with examples was provided to help ensure participants knew what foods contained saturated fat prior to being asked about the saturated fat in their diets (5).
Table 1.
Stage of Change for Dietary Saturated Fat Reduction: Baseline Assessment and Stage-Specific Intervention Strategy*
| Stage of Change |
Assessment Criteria | Intervention Strategy |
|---|---|---|
| Precontemplation | Participant not currently reducing saturated fat in diet and/or never has reduced saturated fat in diet and has not thought about changes he/she can make to decrease the amount of saturated fat in his/her diet in the past month. |
|
| Contemplation | Participant not currently reducing saturated fat in diet and/or never has reduced the saturated fat in diet and is not at all or mildly confident that he/she will make changes to decrease the amount of saturated fat in his/her diet in the next month. |
|
| Preparation | Participant not currently reducing saturated fat diet and/or never has reduced the saturated fat in his/her diet and is somewhat or very confident that he/she will make changes to decrease the amount of saturated fat in his/her diet in the next month. |
|
| Action | Participant reports following a low saturated fat diet for the past one to five months. |
|
| Maintenance | Participant reports following a low saturated fat diet for six months or more. |
|
Adapted From: Kristal AR, Glanz K, Curry SJ, Patterson RE. How can stages of change be best used in dietary interventions? J Am Diet Assoc 1999:99:679–684.
For the purpose of analysis, stage of change was categorized in two ways. First, stage of change was dichotomized into maintenance versus other, because those in maintenance have already made diet changes and participants not in maintenance have not yet, or are in the process of, making diet changes. Second, each of the five stages of change was considered as individual strata, because persons in each stage of change have different levels of readiness to change which could uniquely impact the effectiveness of an educational intervention.
Intervention
Both SI and CI participants received a standardized baseline and one-year follow-up evaluation and a brief educational sheet about heart healthy lifestyle developed using United States Health and Human Services messages to 1) avoid tobacco, 2) choose good nutrition including increased fruit and vegetable consumption and maintain a healthy weight, and 3) be more active, at baseline. Personal screening results were not communicated to the CI until the one-year evaluation was complete unless a critical value of a risk factor was identified (in which case the participant and his/her physician were notified).
Screening results were communicated immediately to SI participants at the baseline visit. The SI was based on the 5 A’s construct (assess, advise, agree, assist, arrange) recommended by the Counseling and Behavioral Interventions Work Group of the United States Preventive Services Task Force (27). Personally tailored education and guidelines on how to achieve and maintain risk factor and lifestyle goals was provided to each SI participant.
Diet educational materials and diet counseling strategies for the SI were developed based on published guidelines for applying stages of change to adoption of healthful diets (5, 28–30). Specific diet recommendations were based on TLC diet principles which emphasize dietary saturated fat and cholesterol reduction and adjustment of total caloric intake to maintain desirable body weight/prevent weight gain (1). Self-determined personal goals for diet change were agreed upon between participant and prevention counselor (Table 1).
Counseling was tailored to each SI participant’s baseline stage of change to reduce dietary saturated fat. Prevention counselors were master’s level health educators who received formal instruction in motivational interviewing through both academic coursework and structured training provided by a doctoral level certified health education specialist. Once stage of change was determined, motivational interviewing techniques were used to deliver education messages to the SI group (6, 31). Key motivational interviewing methods utilized in the SI include asking open ended questions (e.g. “what barriers to reducing the saturated fat in your diet have you experienced in the past, or anticipate facing now?”) and affirming and supporting the participant during the counseling process (e.g. “It is great that you took the step to come in to learn more about your heart disease risk factors and ways to improve them through lifestyle changes.”) (6).
At the end of the baseline screening and education visit, prevention counselors sent risk factor screening results to each SI participant’s primary physician using a standardized form. If a participant did not have a primary physician, the prevention counselor assisted him/her with identifying one and sent results. Prevention counselors conducted five pre-scheduled follow-up phone calls at two weeks, six weeks, three months, six months, and nine months after enrollment with SI participants. Phone calls were completed using standardized scripts to reinforce goals, assess barriers to meeting goals, answer questions, and assist participants in meeting their goals. Phone calls lasted approximately 10–20 minutes depending on extent of patient questions or needs. An invitation to return to the medical center up to three times (at three, six, and nine months after baseline) for the purpose of follow-up blood lipid assessment with results sent to the participant’s primary physician was provided to SI participants if their LDL-cholesterol was above optimal (≥100mg/dL). All baseline measures were repeated at the one-year follow-up evaluation in both the SI and CI groups. At the end of one year SI and CI participants received their screening results and counseling and referral for medical follow-up where indicated. Baseline and one year visits and follow-up visits were observed, and phone calls were monitored routinely and at random, by the principal investigator and study coordinator to ensure quality control.
Statistical Analysis
Descriptive data are presented as means for continuous variables and proportions for categorical variables. For primary outcome (change in saturated fat intake from baseline to one-year), the t-test was used to determine whether there was a difference in the mean individual change in percent of calories from saturated fat from baseline to one-year in the SI versus CI group overall and within stage of change subgroups. Linear regression was used to model the association between group assignment and change in saturated fat intake from baseline to one-year, to adjust for stage of change and other covariates, and to test for interaction between group assignment and stage of change. These procedures were repeated for each continuous diet change outcome.
Chi square statistics were used to determine whether there was a difference in proportion adherent to a Step I Diet by group assignment and stage of change at one-year. Movement along the continuum of stages of change was assessed by comparing stage of change at baseline to stage of change at one-year. The chi-square statistic was used to assess for differences in movement along the continuum (forward, backward, or neutral) by group assignment. Analyses were performed using SAS statistical software (Version 9.1, 2002–2003; SAS Institute, Cary, NC). A two-sided alpha error of < 0.05 indicated statistical significance.
RESULTS
Characteristics of study participants are shown in Table 2. Participants with complete diet data at baseline and 1-year (n=403) were included in the analysis and did not differ from the entire study sample based on baseline characteristics including demographics, stage of change, and diet. At baseline, 55% of participants were in precontemplation, contemplation, preparation, or action stages of change and 45% were in the maintenance stage of change.
Table 2.
Baseline Characteristics of FIT Heart Study Participants (n=403)*
| Characteristic | Special Intervention (n=198) n (%) |
Control Intervention (n=205) n (%) |
|---|---|---|
| Age (≥55 years (F)/≥45 years (M)) | 91 (46) | 91 (44) |
| Female | 135 (68) | 140 (68) |
| Non-white race/ethnicity | 75 (38) | 73 (36) |
| Single/Widowed/Divorced | 69 (35) | 64 (31) |
| Education ≤ high school | 45 (23) | 39 (19) |
| No health insurance | 29 (15) | 27 (13) |
| Family history of premature CHD | 106 (54) | 103 (50) |
| Framingham risk ≥10% | 17 (9) | 18 (9) |
| BMI ≥ 25kg/M2 | 121 (61) | 130 (63) |
| Saturated fat ≥10% of kcals/day | 112 (57) | 122 (60) |
| Statin therapy | 28 (14) | 33 (16) |
| Stage of Change: | ||
| Pre-contemplation | 35 (18) | 36 (18) |
| Contemplation | 7 (4) | 15 (7) |
| Preparation | 32 (16) | 38 (19) |
| Action | 34 (17) | 26 (13) |
| Maintenance | 90 (45) | 90 (44) |
No statistically significant differences in baseline characteristics by group assignment
Baseline diet did not differ by group assignment. Participants were consuming over 10% of calories from saturated fat and exceeding 200mg dietary cholesterol/day on average. Baseline diet by stage of change is presented in Table 3. Dietary saturated fat and cholesterol intake was lower, and fruit and vegetable consumption was higher, among those in maintenance stage versus other stages.
Table 3.
Baseline Diet by Stage of Change among FIT Heart Participants
| Baseline Stage of Change | |||
|---|---|---|---|
| Maintenance n=180 mean (SD) |
Pre-contemplation, Contemplation, Preparation, or Action n=223 mean (SD) |
p | |
| Saturated fat (%kcals) | 9.9 (2.3) | 11.2 (2.7) | <.0001 |
| Cholesterol (mg/1000kcals) | 112.2 (43.0) | 129.7 (53.7) | .0003 |
| MEDFICTS Score1 | 35.7 (21.5) | 55.0 (28.9) | <.0001 |
| Monounsaturated fat (%kcals) | 14.9 (3.6) | 15.1 (3.2) | .72 |
| Polyunsaturated fat (%kcals) | 9.1 (3.0) | 9.2 (2.6) | .84 |
| Trans fat (%kcals) | 2.4 (1.1) | 2.6 (1.1) | .16 |
| Fruit & Vegetable (servings/day) | 5.3 (2.5) | 4.5 (2.4) | .001 |
| Calories | 1852 (663) | 2006 (702) | .03 |
| number (%) | number (%) | ||
| Step I Diet Adherence | 89 (49) | 66 (30) | <.0001 |
| TLC2 Diet Adherence | 13 (7) | 8 (4) | .10 |
MEDFICTS (Meats, Eggs, Dairy, Fried foods, fat In baked goods, Convenience foods, fats added at the Table and Snacks) Score ranges from 0–216 and is correlated with dietary saturated fat and cholesterol intake (14).
Therapeutic Lifestyle Changes
Unadjusted mean changes in dietary saturated fat, cholesterol, and other diet components from baseline to one-year by group assignment are presented in Table 4. Reduction in dietary cholesterol and MEDFICTS score was greater in the SI versus CI. SI participants reduced their saturated fat and trans fat intake almost twice as much as CI participants at one-year. However, between-group differences in reductions were not statistically significant.
Table 4.
Dietary Changes from Baseline to 12 Month Endpoint among FIT Heart Participants
| Change in Diet (baseline to 1-year) |
Between Group Difference in Mean Change |
||
|---|---|---|---|
| Special Intervention n=198 mean (SD) |
Control Intervention n=205 mean (SD) |
P | |
| Saturated fat (%kcals) | −0.7 (2.2) | −0.4 (2.4) | .18 |
| Cholesterol (mg/1000kcals) | −9.5 (55.5) | +4.2 (43.9) | .006 |
| MEDFICTS Score1 | −13.8 (22.2) | −8.3 (21.0) | .01 |
| Monounsaturated fat (%kcals) | −0.04 (3.7) | −0.4 (3.3) | .29 |
| Polyunsaturated fat (%kcals) | −0.2 (3.0) | −0.4 (2.9) | .58 |
| Trans fat (%kcals) | −0.3 (1.2) | −0.1 (0.9) | .18 |
| Fruit & Vegetable (servings/day) | −0.1 (1.9) | 0.0 (2.3) | .64 |
| Calories2 | −309.9 (628) | −300 (589) | .90 |
MEDFICTS (Meats, Eggs, Dairy, Fried foods, fat In baked goods, Convenience foods, fats added at the Table and Snacks) Score ranges from 0–216 and is correlated with dietary saturated fat and cholesterol intake (14).
Among those with BMI ≥ 25
Change in diet from baseline to one-year within each stage of change stratum is presented in Table 5. Participants in precontemplation did not achieve significantly different changes in diet from baseline to one-year by group assignment, however reduction in dietary saturated fat was two-fold as great in the SI versus CI.
Table 5.
Dietary Changes during the Twelve Month Intervention by Group Assignment among FIT Heart Participants: Stratified Analysis by Stage of Change1
| Precontemplation | Contemplation | Preparation | Action | Maintenance | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Special Intervention n=35 mean (SD) |
Control Intervention n=36 mean (SD) |
Special Intervention n=7 mean (SD) |
Control Intervention n=15 mean (SD) |
Special Intervention n=32 mean (SD) |
Control Intervention n=38 mean (SD) |
Special Intervention n=34 mean (SD) |
Control Intervention n=26 mean (SD) |
Special Intervention n=90 mean (SD) |
Control Intervention n=90 mean (SD) |
|
|
Saturated fat (%kcals) |
−1.0 (2.6) | −0.5 (2.7) | −2.1 (2.2) | +0.3 (2.4)* | −0.8 (2.4) | −1.1 (2.8) | −0.7 (2.2) | +0.3 (2.3) | −0.4 (2.0) | −0.3 (2.2) |
|
Cholesterol (mg/1000kcals) |
−19.9 (61.7) | +3.9 (47.2) | −34.0 (44.7) | +32.6 (54.0)* | −2.2 (68.5) | −2.2 (41.1) | −16.1 (57.9) | +17.7 (45.0)* | −5.1 (46.6) | −1.5 (39.6) |
| MEDFICTS2 Score | −12.9 (23.9) | −8.8 (19.8) | −21.9 (29.9) | −17.6 (19.3) | −23.9 (27.3) | −14.8 (30.3) | −14.6 (18.6) | −6.0 (21.4) | −9.5 (19.0) | −4.5 (15.3) |
|
Monounsaturated fat(%kcals) |
−0.9 (3.9) | −0.8 (2.9) | −1.8 (3.0) | +0.2 (2.6) | −0.6 (2.6) | −0.3 (3.1) | +0.1 (4.1) | −0.4 (4.0) | +0.6 (3.7) | −0.4 (3.6) |
|
Polyunsaturated fat(%kcals) |
−0.2 (3.3) | −1.2 (3.0) | −0.5 (1.8) | −0.8 (3.1) | −0.4 (3.1) | −0.4 (2.9) | −1.0 (2.7) | −0.04 (2.6) | +0.1 (3.0) | −0.1 (2.8) |
| Trans fat (%kcals) | −0.3 (1.3) | −0.1 (1.0) | −1.0 (1.0) | −0.1 (1.1) | −0.1 (1.0) | −0.2 (0.9) | −0.3 (0.9) | +0.1 (0.8) | −0.2 (1.3) | −0.1 (0.9) |
|
Fruit & Vegetable (servings/day) |
+0.5 (1.6) | −0.4 (2.6) | −0.5 (0.9) | +.13 (1.4) | +0.2 (1.8) | +0.1 (1.8) | −0.6 (2.0) | −0.7 (1.5) | −0.2 (2.0) | +0.3 (2.7) |
| Calories3 | −180 (726) | −400 (674) | −682 (655) | −330 (656) | −432 (682) | −448 (708) | −209 (426) | −256 (468) | −276 (625) | −179 (485) |
Univariate results stratified by stage of change
MEDFICTS (Meats, Eggs, Dairy, Fried foods, fat In baked goods, Convenience foods, fats added at the Table and Snacks) Score ranges from 0–216 and is correlated with dietary saturated fat and cholesterol intake (14).
Where baseline BMI ≥ 25
p < .05
SI participants in the contemplation stage at baseline achieved significant reductions in both saturated fat and cholesterol intake from baseline to one-year compared to CI. The SI reduced saturated fat by more than two percent of calories on average. Multivariable regression models showed statistically significant interaction between contemplation stage of change and SI group assignment after adjustment for age group, gender, race/ethnicity, family history of premature CVD in a blood relative, education level, overweight/obesity, and baseline saturated fat intake; SI participants in the contemplation stage of change at baseline (n=7) had reductions in saturated fat and cholesterol intakes that exceeded what would be expected based on stage of change and group assignment alone (Beta for interaction=−2.6; p=.007 (saturated fat) and =−62.8; p=.001 (cholesterol)).
Preparation stage participants in the SI and CI all achieved reductions in dietary fat, cholesterol, and MEDFICTS score, but there were no differences between groups in magnitude of change. SI participants in the action stage at baseline achieved significantly greater reductions in dietary cholesterol and borderline significant greater reductions in percent of calories from saturated fat (−0.7 vs. +0.3;p=.07) and MEDFICTS score (−14.6 vs. −6.0;p=.10) from baseline to one-year compared to CI participants in action. However, there was no significant interaction between action stage of change and SI group assignment on change in diet from baseline to one-year. No significant differences in diet change in the SI versus CI were observed among participants in maintenance stage at baseline.
Adherence to a Step I diet at one-year was higher among those in the maintenance stage at baseline compared to those who were not (56% vs. 38%;p=.0005). Among participants not in maintenance and non-adherent to the Step I diet at baseline (n=157), those assigned to the SI were more likely to achieve adherence to the Step I diet at one-year compared to those randomized to the CI (30% vs. 15%;p=.03).
More than half of participants were in a different stage of change at one-year compared to baseline. Movement to higher stages was achieved by 40% of participants, and 12% reverted to lower stages of change at one-year (e.g. from maintenance back to contemplation). Significantly more CI participants reverted to lower stages compared to SI participants (CI=17% vs. SI=7%;p=.002). Age, gender, race/ethnic group, education level, baseline BMI, and baseline diet were not significantly associated with backwards movement across stages from baseline to one-year. Proportionately more SI participants moved forward across stages (i.e. moved towards action and maintenance) compared to CI from baseline to one-year. However, this difference did not reach statistical significance (SI=44% vs. CI=35%; p=.07).
DISCUSSION
In this randomized controlled trial, SI participants in the contemplation stage at baseline experienced greater saturated fat and cholesterol reductions relative to SI participants in other stages and controls. SI participants not in maintenance were more likely to improve adherence to a Step I diet, and SI participants were less likely to revert to lower stage of change from baseline to one-year compared to controls. These results suggest that a stage of change-matched educational intervention was effective to promote desirable diet changes and effectiveness may be modified by baseline stage of change.
In this study, there was almost an even split of participants between the maintenance stage and other stages, which is similar to distributions documented in the United States (U.S.) population (32). Interestingly, there were fewer participants in precontemplation and more in preparation and action stages relative to those reported previously in the U.S. This could reflect increased awareness about the role saturated fat plays in CVD risk among CVD patient family members compared to the general population.
Participants in the maintenance stage of change at baseline had lower baseline saturated fat and cholesterol intake levels compared to participants not in maintenance. This result supports the internal validity of the stage of change questionnaire to correctly categorize participants; to be classified in maintenance stage, participants reported that they had already made reductions in saturated fat intake for more than six months prior to their baseline visit and were trying to sustain them (33–34).
Among participants in precontemplation and contemplation at baseline, there was more than a two-fold greater reduction in saturated fat and cholesterol in the SI versus CI from baseline to one-year, however not all comparisons were statistically significant, possibly due to limited sample size within strata. The magnitude of the difference in saturated fat reduction between groups could be clinically relevant. It is estimated that reduction in dietary saturated fat by 1% of calories will promote a decrease in blood cholesterol of approximately 2% (1, 35). The small number of participants in the contemplation stage at baseline may have been a result of the strict definition and short time window for this stage of change. Persons who are in contemplation may have greater potential to achieve diet changes if moved along to preparation and action, because they have not made changes before.
Recent research examining the effects of targeted health messages toward reducing fat consumption supports this and has shown that individuals within each stage of change have unique profiles related to behavioral determinants such as affect, and outcome expectancy (36). Combining stages to increase within-category sample size could have resulted in lost information specific to each individual stage of change. Therefore, stratum-specific results were reported, despite a modest sample size in the contemplation stage. Results indicating that contemplation stage was a modifier of the intervention effect are consistent with other research showing stage-tailored behavioral counseling is helpful in overcoming barriers to diet change among program participants in the contemplation stage of diet change (37).
CI participants were more likely than SI participants to revert backward across stages of change, which may explain the average increase in saturated fat, dietary cholesterol, and trans fat intake documented at one-year among CI participants in action stage at baseline. These results support the hypothesis that diet change follows a staged process and that movement through stages may illustrate the effectiveness of a program to promote diet change (5). This argues for providing a stage-based intervention to participants in all stages of change, to prevent worsening of diet and/or reduction in readiness to make diet changes.
FIT Heart is not the first randomized controlled trial to incorporate the Transtheoretical Model into its educational intervention. For example, past research has shown brief nurse-administered behavioral counseling based on the stages of change to be successful to reduce dietary fat consumption over one year among persons at increased CVD risk (38). More recently, ALIVE! (A Lifestyle Intervention Via Email), a web-based intervention designed to improve diet and physical activity including an intervention incorporating the Transtheoretical Model of behavior change was evaluated (39). Four months after randomization, significantly larger reductions in saturated fat and trans fat intake and greater increases in fruit and vegetable consumption, were reported by ALIVE! intervention participants compared with controls (40). FIT Heart may be the first family targeted CVD risk intervention to incorporate the Transtheoretical Model.
The FIT Heart study utilized motivational interviewing techniques in person and over the telephone. Results were consistent with those from other studies which have shown motivational interviewing interventions to produce desired diet changes, especially as the number of encounters (in person and/or over the telephone) increases (41).
Strengths of this study include participation by females and racial/ethnic minorities which increases generalizability of results, detailed diet assessment, and high rate of follow up at one-year. Because of small sample size within stage of change strata, power to detect significant differences in diet change between groups that may have been clinically relevant may have been limited. In addition, self-reported diet behavior is subject to recall bias and could differ by stage of change. However, use of highly trained interviewers and validated questionnaires makes this less likely (and unlikely to be differential by group assignment). Moreover, it has been established that lipid changes were consistent with self-reported diet changes in this study population. Stage of change is a dynamic process and participants could have moved through several stages of change over the course of one year; however, successful randomization resulted in equal distribution of baseline stage of change between groups making it unlikely that any observed difference in movement through stages of change between the intervention and control groups is attributable to factors other than the intervention.
In conclusion, study results suggest that effectiveness of a stage of change matched educational intervention varies by baseline stage of change. This may be important to consider when designing research or clinical diet interventions. Future research is needed to create and test diet interventions effective to promote desirable diet changes and maintenance of heart healthy diets among persons at all stages of change.
Footnotes
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