title: Exercise or exercise and diet for preventing type 2 diabetes mellitus.
abstract: BACKGROUND
  The incidence of type 2 diabetes is associated with the 'Westernised lifestyle', mainly in terms of dietary habits and physical activity. Thus an intensive diet and exercise intervention might prevent or delay the appearance of diabetes in persons at high risk.
  
  
  OBJECTIVE
  To assess the effects of exercise or exercise and diet for preventing type 2 diabetes mellitus.
  
  
  METHODS
  We searched The Cochrane Library, MEDLINE, EMBASE, CINAHL, LILACS, SocioFile, databases of ongoing trials and reference lists of relevant reviews.
  
  
  METHODS
  Studies were included if they were randomised controlled trials of exercise and diet interventions of at least six month duration and reported diabetes incidence in people at risk for type 2 diabetes.
  
  
  METHODS
  Two authors independently assessed trial quality and extracted data. Study authors were contacted to obtain missing data. Data on diabetes incidence and secondary outcomes were analysed by means of random-effects meta-analysis.
  
  
  RESULTS
  We included eight trials that had an exercise plus diet (2241 participants) and a standard recommendation arm (2509 participants). Two studies had a diet only (167 participants) and exercise only arm (178 participants). Study duration ranged from one to six years. Overall, exercise plus diet interventions reduced the risk of diabetes compared with standard recommendations (RR 0.63, 95% CI 0.49 to 0.79). This had also favourable effects on weight and body mass index reduction, waist-to-hip ratio and waist circumference. However, statistical heterogeneity was very high for these outcomes. Exercise and diet interventions had a very modest effect on blood lipids. However, this intervention improved systolic and diastolic blood pressure levels (weighted mean difference -4 mmHg, 95% CI -5 to -2 and -2 mmHg, 95% CI -3 to -1, respectively). No statistical significant effects on diabetes incidence were observed when comparing exercise only interventions either with standard recommendations or with diet only interventions. No study reported relevant data on diabetes and cardiovascular related morbidity, mortality and quality of life.
  
  
  CONCLUSIONS
  Interventions aimed at increasing exercise combined with diet are able to decrease the incidence of type 2 diabetes mellitus in high risk groups (people with impaired glucose tolerance or the metabolic syndrome). There is a need for studies exploring exercise only interventions and studies exploring the effect of exercise and diet on quality of life, morbidity and mortality, with special focus on cardiovascular outcomes.
authors.affiliation: Dept. of Endocrinology & Nutrition, Hospital Universitari Arnau de Vilanova, Rovira Roure, 80, Lleida, Spain, 25198.
authors.forename: Leonardo J
authors.initials: LJ
authors.lastname: Orozco
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Buchleitner
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gimenez-Perez
authors.forename: Marta
authors.initials: M
authors.lastname: Roqué I Figuls
authors.forename: Bernd
authors.initials: B
authors.lastname: Richter
authors.forename: Didac
authors.initials: D
authors.lastname: Mauricio
mesh_terms: D003131:Combined Modality Therapy / Q000379:methods; D003924:Diabetes Mellitus, Type 2 / Q000517:prevention & control*; D004032:Diet; D003927:Diet, Diabetic; D015444:Exercise; D006801:Humans; D016032:Randomized Controlled Trials as Topic