title: Carbohydrate intake, obesity, metabolic syndrome and cancer risk? A two-part systematic review and meta-analysis protocol to estimate attributability.
abstract: BACKGROUND
  Linkages between carbohydrates, obesity and cancer continue to demonstrate conflicting results. Evidence suggests inconclusive direct linkages between carbohydrates and specific cancers. Conversely, obesity has been strongly linked to a wide range of cancers. The purpose of the study is to explore linkages between carbohydrate intake and cancer types using a two-step approach. First the study will evaluate the linkages between carbohydrate intake and obesity, potentially stratified by metabolic syndrome status. Second, the estimated attributable fraction of obesity ascribed to carbohydrate intake will be multiplied against obesity attributable fractions for cancer types to give estimated overall attributable fraction for carbohydrate versus cancer type.
  
  
  METHODS
  We will perform a comprehensive search to identify all possible published and unpublished studies that have assessed risk factors for obesity including dietary carbohydrate intake. Scientific databases, namely PubMed MEDLINE, EMBASE, EBSCOhost and ISI Web of Science will be searched. Following study selection, paper/data acquisition, and data extraction and synthesis, we will appraise the quality of studies and risk of bias, as well as assess heterogeneity. Meta-weighted attributable fractions of obesity due to carbohydrate intake will be estimated after adjusting for other potential confounding factors (eg, physical inactivity, other dietary intake). Furthermore, previously published systematic reviews assessing the cancer-specific risk associated with obesity will also be drawn. These estimates will be linked with the attributability of carbohydrate intake in part 1 to estimate the cancer-specific burden that can be attributed to dietary carbohydrates. This systematic review protocol has been developed according to the 'Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) 2015'.
  
  
  BACKGROUND
  The current study will be based on published literature and data, and, as such, ethics approval is not required. The final results of this two part systematic review (plus multiplicative calculations) will be published in a relevant international peer-reviewed journal.
  
  
  BACKGROUND
  PROSPERO CRD42015023257.
authors.affiliation: Discipline of Public Health Medicine, School of Nursing and Public Health, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa University of KwaZulu-Natal Gastrointestinal Cancer Research Centre (GICRC), Durban, KwaZulu-Natal, South Africa.
authors.forename: B
authors.initials: B
authors.lastname: Sartorius
authors.affiliation: Discipline of Public Health Medicine, School of Nursing and Public Health, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa University of KwaZulu-Natal Gastrointestinal Cancer Research Centre (GICRC), Durban, KwaZulu-Natal, South Africa Faculty of Commerce, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: K
authors.initials: K
authors.lastname: Sartorius
authors.affiliation: University of KwaZulu-Natal Gastrointestinal Cancer Research Centre (GICRC), Durban, KwaZulu-Natal, South Africa School of Clinical Medicine, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa.
authors.forename: C
authors.initials: C
authors.lastname: Aldous
authors.affiliation: University of KwaZulu-Natal Gastrointestinal Cancer Research Centre (GICRC), Durban, KwaZulu-Natal, South Africa School of Clinical Medicine, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa.
authors.forename: T E
authors.initials: TE
authors.lastname: Madiba
authors.affiliation: University of KwaZulu-Natal Gastrointestinal Cancer Research Centre (GICRC), Durban, KwaZulu-Natal, South Africa South African Medical Research Council, Cape Town, South Africa.
authors.forename: C
authors.initials: C
authors.lastname: Stefan
authors.affiliation: Division of Exercise Science and Sports Medicine, University of Cape Town.
authors.forename: T
authors.initials: T
authors.lastname: Noakes
mesh_terms: D015897:Comorbidity; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D006801:Humans; D024821:Metabolic Syndrome / Q000453:epidemiology*; D009369:Neoplasms / Q000453:epidemiology*; D009765:Obesity / Q000453:epidemiology*; D012307:Risk Factors; D000078202:Systematic Reviews as Topic; D015201:Meta-Analysis as Topic
chemical_list: D004040:Dietary Carbohydrates
keywords: DIABETES & ENDOCRINOLOGY; EPIDEMIOLOGY; NUTRITION & DIETETICS; ONCOLOGY; PUBLIC HEALTH; STATISTICS & RESEARCH METHODS