Important Food Sources of Fructose-Containing Sugars and Markers of Adiposity and Risk of Obesity: A Series of Systematic Reviews and Meta-Analyses of Controlled Trials and Prospective Cohort Studies

Background: Sugars have emerged as one of the most important public health concerns. Attention has focused squarely on fructose-containing sugars (fructose, sucrose, high fructose corn syrup [HFCS], etc.). Collectively, these sugars have been indicted as drivers of the obesity epidemic and its and its downstream cardiometabolic complications. This special view rests on the unique metabolic and endocrine responses to fructose. Unlike glucose, fructose is thought to bypasses negative feedback control acting as an unregulated substrate for de novo lipogenesis and impair satiety signaling resulting in weight gain. In support of these mechanisms, animal models, low-quality ecological studies, and select human trials of overfeeding at levels of exposure far beyond population intakes have reported adverse metabolic effects of sugars. Higher level evidence from systematic reviews and meta-analyses of controlled trials, however, suggests that any effects of sugars are mediated by excess calories rather than the sugars per se. There is also evidence that not all food sources of these sugars are associated equally with obesity. While sugars-sweetened beverages (SSBs) have shown an adverse association with body weight, markers of adiposity and obesity, other important food sources of sugars such as fruit, 100% fruit juice, cereals, yogurts, and even cakes/sweets have shown either no association or a beneficial association. It remains unclear whether sugars contribute to weight gain or increases in adiposity independent of their calories and whether important food sources other than SSBs are associated with a higher risk of overweight and obesity.

Need for proposed research: High quality systematic reviews and meta-analyses of controlled trials and prospective cohort studies represent the highest level of evidence to support dietary guidelines and public health policy development. As dietary guidelines and public health policy have shifted toward food and dietary-pattern based recommendations, there is an urgent need for systematic reviews and meta-analyses comparing the role of different food sources of sugars in the development of overweight and obesity.

Objective: The investigators will conduct a series of American Society of Nutrition (ASN)-commissioned systematic reviews and meta-analyses to assess (1) the effect of different important food sources of sugars (e.g. SSBs, fruit, 100% fruit juice, yoghurt, cereals, cakes, pastries, sweets, etc.) at different levels of energy control on body weight and markers of adiposity in controlled trials and (2) their association with incident overweight/obesity and markers of adiposity in prospective cohort studies.

Design: Each systematic review and meta-analysis will be conducted according to the Cochrane Handbook for Systematic Reviews of Interventions and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Data sources: MEDLINE, EMBASE, and The Cochrane Central Register of Controlled Trials (Clinical Trials; CENTRAL) will be searched using appropriate search terms supplemented by hand searches of references of included studies.