BMI as a cofounder or mediator in relation between sugar sweetened beverages and type 2 diabetes biomarkers: An overadjustment in cross-sectional study?

Abstract

We read with great interest the work of Lazzinnaro et al. [ [1] Lazzinnaro R. Plourde H. Johnson-Down L. Dewailly E. Egeland G.M. High-sugar drink consumption: an associate of obesity and impaired fasting glucose in Canadian indigenous (Cree) communities. Nutr Metab Cardiovasc Dis. 2012; Google Scholar ] among Canadian Indigenous Cree. Sugar sweetened beverages (SSB) consumption has increased dramatically in various populations, and has associated to increased risks of weight gain, obesity and type 2 diabetes (T2D) [ 2 Malik V.S. Popkin B.M. Bray G.A. Despres J.P. Willett W.C. Hu F.B. Sugar-sweetened beverages and risk of metabolic syndrome and type 2 diabetes: a meta-analysis. Diabetes Care. 2010; 33: 2477-2483 Crossref PubMed Scopus (1368) Google Scholar , 3 Malik V.S. Popkin B.M. Bray G.A. Despres J.P. Hu F.B. Sugar-sweetened beverages, obesity, type 2 diabetes mellitus, and cardiovascular disease risk. Circulation. 2010; 121: 1356-1364 Crossref PubMed Scopus (1106) Google Scholar , 4 Malik V.S. Willett W.C. Hu F.B. Sugar-sweetened beverages and BMI in children and adolescents: reanalyses of a meta-analysis. Am J Clin Nutr. 2009; 89 ([author reply 439–40]): 438-439 Crossref PubMed Scopus (156) Google Scholar , 5 Mozaffarian D. Hao T. Rimm E.B. Willett W.C. Hu F.B. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011; 364: 2392-2404 Crossref PubMed Scopus (1620) Google Scholar ]. Therefore, exploring the underlying mechanisms is of great scientific interest and of public health importance [ [6] Hu F.B. Malik V.S. Sugar-sweetened beverages and risk of obesity and type 2 diabetes: epidemiologic evidence. Physiol Behav. 2010; 100: 47-54 Crossref PubMed Scopus (556) Google Scholar ]. In their analyses, Lazzinnaro et al. [ [1] Lazzinnaro R. Plourde H. Johnson-Down L. Dewailly E. Egeland G.M. High-sugar drink consumption: an associate of obesity and impaired fasting glucose in Canadian indigenous (Cree) communities. Nutr Metab Cardiovasc Dis. 2012; Google Scholar ] reported that frequent SSB consumption was associated with higher BMI, greater insulin resistance (IR), and increased odds of having impaired fasting glucose (IFG). However, the results for IR and IFG may have been attenuated with adjustment of BMI in the model, given the concern that BMI could be a potential intermediator for the association between SSB consumption and IR/IFG. Thus, it would be also interesting to show the results without adjustment of BMI in the model. Furthermore, as the authors reported in the letter, 64% of the participants were obese, it is also of interest to assess whether there is an interaction between SSB consumption and BMI in the relation to IR/IFG (i.e., obese people who frequently drink SSB would have a much higher risk of having IR/IFG). Finally, given the nature of cross-sectional study design, reverse causation is possible and the direction of the association could not be determined.