Objective: To compare health benefits achieved in a transtheoretical model-chronic disease (TM-CD) minimal intervention for obesity vs. augmented usual care (AUC).
Research method and procedures: This was a 2-year, randomized clinical trial with overweight or obese men and women from 15 primary care sites. AUC (n = 336) included dietary and exercise advice, prescriptions, and three 24-hour dietary recalls every 6 months. TM-CD care (n = 329) included AUC elements plus "stage of change" (SOC) assessments for five target behaviors every other month, mailed SOC and target behavior-matched workbooks, and monthly telephone calls from a weight-loss advisor. Weight change was the primary outcome.
Results: Repeated measures models under the missing at random assumption yielded nonsignificant adjusted differences between the AUC and TM-CD groups for weight change, waist circumference, energy intake or expenditure, blood pressure, and blood lipids. The pattern of change over time suggested that TM-CD participants were trying harder to impact target behaviors during the first 6 to 12 months of the trial but relapsed afterward. Sixty percent of trial participants maintained their baseline weights for 18 to 24 months.
Discussion: A combination of mailed patient materials and monthly telephone calls based on the transtheoretical model and some elements of chronic disease care is not powerful enough, relative to AUC, to alter target behaviors among overweight primary care patients in an obesogenic environment. AUC may be sufficient to maintain weights among at-risk primary care patients.