Background: Most persons with prediabetes (impaired glucose tolerance or impaired fasting glucose) are overweight, and obesity worsens the metabolic and physiologic abnormalities associated with this condition. Prediabetes is an important risk factor for the development of type 2 diabetes.
Objectives: The objective of this review was to assess the effectiveness of dietary, physical activity, and behavioral weight loss, and weight control interventions for adults with prediabetes.
Search strategy: Studies were obtained from computerized searches of multiple electronic bibliographic databases, supplemented by hand searches of selected journals, and consultation with experts in obesity research. The last search was conducted May, 2004.
Selection criteria: Studies were included if they were published or unpublished randomized controlled trials in any language and examined weight loss or weight control strategies using one or more dietary, physical activity, or behavioral interventions, with a follow-up interval of at least 12 months.
Data collection and analysis: Effects were combined using a random-effects model.
Main results: Nine studies were identified, with a total of 5,168 participants. Follow-up ranged from 1 to 10 years. Quantitative synthesis was limited by the heterogeneity of populations, settings, and interventions and by the small number of studies that examined outcomes other than weight. Overall, in comparisons with usual care, four studies with a follow-up of one year reduced weight by 2.8 kg (95 % confidence interval (CI) 1.0 to 4.7) (3.3% of baseline body weight) and decreased body mass index by 1.3 kg/m(2) (95% CI 0.8 to 1.9). Weight loss at two years was 2.6 kg (95% CI 1.9 to 3.3) (three studies). Modest improvements were noted in the few studies that examined glycemic control, blood pressure, or lipid concentrations (P > 0.05). No data on quality of life or mortality were found. The incidence of diabetes was significantly lower in the intervention groups versus the controls in three of five studies examining this outcome at 3 to 6 years follow-up.
Authors' conclusions: Overall, weight loss strategies using dietary, physical activity, or behavioral interventions produced significant improvements in weight among persons with prediabetes and a significant decrease in diabetes incidence. Further work is needed on the long-term effects of these interventions on morbidity and mortality and on how to implement these interventions in diverse community settings.