Objectives: Adults tend to gain weight progressively through middle age. Although the average weight gain is 0.5 to 1 kg per year, this modest accumulation of weight can lead to obesity over time. We aimed to compare the effectiveness, safety, and impact on quality of life of strategies to prevent weight gain among adults. Self-management, dietary, physical activity, orlistat and combinations of these strategies were considered.
Data sources: We searched MEDLINE®, Embase®, the Cochrane Central Register of Controlled Trials, CINAHL®, and PsycINFO® through June 2012 for published articles that were potentially eligible for this review.
Review methods: Two reviewers independently reviewed titles, abstracts, and articles, and included English-language articles that reported on maintenance of weight or prevention of weight gain among adults. Studies targeting a combination of weight loss with weight maintenance or weight loss exclusively were considered to be outside of the scope of this review. Trials of interventions and observational studies of approaches with at least 1 year of followup with a weight outcome were included. Data were abstracted on measures of weight, adherence, obesity-related outcomes, safety, and quality of life. The timepoints of interest for weight outcomes were: 1 year, 2 years, 5 years, and the last reported timepoint after 5 years. For the other outcomes, we abstracted data only from the last reported timepoint on or after 1 year. We selected a meaningful difference threshold in addition to a statistically significant threshold (p<0.05) for the outcomes. A meaningful between group difference was defined as 0.5 kg of weight, 0.2 units of BMI (based on a 0.5-kg change for an individual with a BMI of 27), or 1 cm of waist circumference per year of followup. We considered an intervention or approach effective if the difference between groups met the meaningful between group difference threshold and was statistically significant. We qualitatively synthesized the studies by population, intervention, and outcome.
Results: We included 58 publications (describing 51 studies) involving 555,783 patients. Two interventions may be effective compared with no intervention at preventing weight gain with moderate strengths of evidence: workplace interventions having individual and environmental components and exercise performed at home by women with cancer. Potentially effective interventions with low strength of evidence include a clinic-based program to teach heart rate monitoring, a combination intervention for mothers of young children, small group sessions to educate college women, and physical activity among individuals at risk of cardiovascular disease and diabetes. Potentially effective approaches described in observational studies having low strength of evidence include eating meals prepared at home among college graduates and less television viewing among individuals with colorectal cancer. When reported, adherence to interventions tended to be below 80 percent. There were no adverse events among the few trials that reported on adverse events. Trial study quality tended to be poor due to knowledge of the intervention by the study personnel who measured the weight of the participants or lack of reporting on this item. This lack of blinding of the outcome assessor along with inclusion of studies that were not designed to prevent weight gain resulted in a low strength of evidence for the majority of comparisons.
Conclusions: The literature provides some, although limited, evidence about interventions and approaches that may prevent weight gain. Although there is not strong evidence to promote a particular weight gain prevention strategy, there is no evidence that not adopting a strategy to prevent weight gain is preferable.