OBJECTIVE: To examine stage-matched nutrition counseling by family physicians and its effect on dietary intake, anthropometry, and serum lipid levels in patients at elevated risk for cardiovascular disease.
METHODS: In this controlled trial, patients randomized to intervention practices received nutrition information following the Stages-of-Change Model, and patients randomized to control practices received usual care.
RESULTS: At both 6 and 12 months after baseline, total fat intake and saturated fat intake declined significantly more in the intervention group than in the control group: -5.7% and -2.6% of energy, respectively, at 6 months, and -3.6% and -1.7% of energy, respectively, at 12 months. For energy intake, body weight, and BMI, there were significant differences between groups only at 6 months: -0.8 megajoules (MJ), -0.7 kg, and -0.3 kg/m2, respectively. None of the serum lipid values changed significantly between groups at 12 months.
CONCLUSIONS: Nutritional counseling based on stages of change led to reductions in dietary fat intake and weight loss in the short term. However, we found no corresponding changes in serum lipid concentrations.
- Family physicians can select patients for nutrition counseling by a dietician by using a simple questionnaire based on the Stages-of-Change Model.
- With dietary intervention, a decline in fat intake was sustained at 1 year in a population with a high percentage of poorly educated subjects.
- We found no changes in serum lipids after 1 year of dietary intervention.
Cholesterol-lowering diet therapy is an important part of cardiovascular disease prevention.1 Family physicians (FPs) are uniquely positioned to provide nutrition information to persons at risk because of their expertise as perceived by consumers, and because they reach into nearly all segments of the population.2 It is important to build nutrition guidance into a model that enables change, and, considering the number of contacts between FP and patient,3,4 that is linked to the FP’s continuity of care over time.5 FPs can raise patient consciousness about dietary behavior, motivate patients to change their behavior, and, when appropriate, refer patients to a dietician or patient associations.6
The Transtheoretical Model of Behavior Change is increasingly being used to examine health behavior change.7 According to this model, people are assigned to 1 of the following 5 stages on the basis of their behavior and current intention for future action: (i) precontemplation, not even considering changing one’s behavior; (ii) contemplation, thinking about it; (iii) preparation, making definite plans to change; (iv) action, initiating behavior change; and (v) maintenance, maintaining desired behaviors.8
Evidence available on dietary applications studied in cross-sectional and not stage-matched intervention studies is sufficiently encouraging to warrant the inclusion of Transtheoretical Model constructs in prospective studies.7 As far as we know, only 2 stage-matched dietary intervention studies have been published. Both studies were carried out in primary care settings and both studies showed that tailored nutrition information is effective in dietary fat reduction.9,10 However, in these studies the intervention was not managed by the FP. We think the FP is the most appropriate person to manage such intervention in the family practice. Therefore, we conducted a controlled dietary intervention, based on the Stages-of-Change Model and managed by the FP with selective referral to a dietician. We examined the effects of dietary counseling on changes in dietary intake, anthropometry, and serum lipid levels in patients at elevated cardiovascular risk.
Participants and design
In this randomized controlled trial, men and women at elevated risk for cardiovascular disease were recruited from the 9 family practices joining the Nijmegen Monitoring Project, the research network of the Department of Family Medicine, University Medical Centre St. Radboud.11 Selection and flow of participants are described in Figure 1. Seventy-one patients were initially included in the intervention group and 72 patients in the control group (Table 1). Consequently, we had enough power (0.90) to detect a difference in change between groups for total fat intake of 3% of energy and 11.6 mg% of serum total cholesterol.12
After selection and recruitment of participants, the family practices were randomly divided into intervention (4) and control (5) practices. The practices, and not the patients, were the units of randomization, to avoid contamination of the information between intervention and control groups. Patients in the control practices received usual care.13-15 Each patient in the intervention arm received nutrition information according to his or her stage of change. All participants signed an informed consent form before entering the study. The Medical Ethical Committee of the Department of Human Nutrition and Epidemiology, Wageningen University, approved the study protocol. The study lasted from August 1998 until April 2000.