Transtheoretical model for dietary and physical exercise modification in weight loss management for overweight and obese adults.

BACKGROUND: Obesity is a global public health threat. The transtheoretical model stages of change (TTM SOC) model has long been considered a useful interventional approach in lifestyle modification programmes, but its effectiveness in producing sustainable weight loss in overweight and obese individuals has been found to vary considerably. 

OBJECTIVES: To assess the effectiveness of dietary and physical activity interventions based on the transtheoretical model, to produce sustainable weight loss in overweight and obese adults.

SEARCH STRATEGY: Studies were obtained from searches of multiple electronic bibliographic databases. Date of last search for The Cochrane Library was issue 10, 2010, for MEDLINE Dezember 2010, for EMBASE January 2011 and for PSYCHINFO Januar 2011.

SELECTION CRITERIA: Trials were included if they fulfilled the following criteria: randomised controlled clinical trials using TTM SOC as a model, theoretical framework or guideline in designing lifestyle modification strategies, mainly dietary and physical exercise versus a comparison intervention of usual care; one of the outcome measures of the study was weight loss; and participants were overweight or obese adults.

DATA COLLECTION AND ANALYSIS: Two researchers independently applied the inclusion criteria to the identified studies and assessed risk of bias. Disagreement was resolved by discussion or by intervention of a third party. Descriptive analysis was conducted for the review.

MAIN RESULTS: A total of five studies met the inclusion criteria and a total of 3910 participants were evaluated. The total number of participants randomised to intervention groups was 1834 and 2076 were randomised to control groups. Overall risk of bias was high. The trials varied in length of intervention from six weeks to 24 months, with a  median length of nine months. The intervention was found to have limited impact on weight loss (about 2 kg or less) and other outcome measures. There was no conclusive evidence for sustainable weight loss. However, TTM SOC and a combination of physical activity, diet and other interventions tended to produce significant outcomes (particularly change in physical activity and dietary intake). TTM SOC was used inconsistently as a theoretical framework for intervention in the trials. Death and weight gain are the two adverse events reported by the included trials. None of the trials reported health-related quality of life, morbidity, and costs as outcomes.

AUTHORS' CONCLUSIONS: TTM SOC and a combination of physical activity, diet and other interventions resulted in minimal weight loss, and there was no conclusive evidence for sustainable weight loss. The impact of TTM SOC as theoretical framework in weight loss management may depend on how it is used as a framework for intervention and in combination with other strategies like diet and physical activities.