Importance of studying added sugars in adolescents. Research that leads to nutritional strategies to prevent T2D in adolescents is an urgent pursuit. One particular contributing factor to the growth of T2D and prediabetes in adolescents is the increased consumption of added sugars. Adolescents in the U.S. have high intakes of added sugars which could have poor health implications. Added sugars are found in sugar sweetened beverages and desserts and snacks, top sources of energy for adolescents, and calories from added sugars contribute to 16% of the total energy intake. Levels are well above recommendations from leading scientific organizations, which suggest limiting added sugars to less than 10% of energy. However, it is not clear whether sugar reduction to less than 10% of energy is palatable for an adolescent population that prefers sweetened foods and beverages. Moreover, uncertainty about the evidence linking added sugar consumption to risk of disease has made policies that seek to reduce dietary intake of added sugar controversial. The controversy impairs large-scale implementation of recommendations to reduce intake of added sugars by individuals, clinicians, policy makers and industry stakeholders.

Evidence linking added sugars and risk of type 2 diabetes and cardiovascular disease lacks information on adolescents. Many epidemiological studies in adults, but not all show the concept that after controlling for energy intake, high consumption of sugar-sweetened foods is a risk factor for T2D. Epidemiological studies also associate high consumption of added sugars, particularly from sugar sweetened beverages (SSB), with increased adiposity (including central adiposity) and dyslipidemia. These studies formed the basis of recommendations to limit added sugar consumption from the American Heart Organization. The data in youth is limited. Two small randomized studies compared the effects of glucose versus fructose beverages on insulin sensitivity in adolescents and findings were mixed. One longitudinal cohort study showed that higher consumption of added sugars, from SSB, was associated with hyperglycemia and impaired insulin sensitivity in youth aged 8 - 12 years. One study showed that high amounts of added sugars may induce insulin resistance and beta-cell dysfunction and such effects can occur independent of adiposity. The literature lacks evidence linking high consumption of added sugars to risk of developing youth-onset T2D.

Substituting Flavored Sparkling Water for Sugar Sweetened Beverages. Instead of sugar, food manufacturers typically sweeten foods beverages using low-calorie or artificial sweeteners. "Diet" versions of SSB have been available for several decades and are widely used by adults and children. However the safety of low calorie sweeteners is controversial and many in the scientific and lay communities do not promote their use as a substitute for SSB. We propose that an alternative to SSB may be found in sparkling waters (carbonated water with flavoring, completely unsweetened), which are commercially available in soda-like flavors like cola or Dr. Pepper™. The rationale for the current project is the urgent need for an effective strategy to combat adolescent T2D which investigators will address by demonstrating the benefit of an intervention to reduce added sugars. The objective of the study is to demonstrate whether substituting sparkling water for SSB has benefits for in vivo physiological measures of glycemia while maintaining flavor acceptability to adolescents who are at risk for diabetes.