The association between dietary sugar and type 2 diabetes (T2D) is likely mediated by the unregulated hepatic metabolism of fructose, which promotes hepatic and whole-body insulin resistance. Experimental evidence from clinical studies that utilize sensitive methods to test the effects of added sugar on insulin sensitivity is required. Establishing a causal link between added sugar and insulin resistance will help to stimulate health policies that target the reduction of added sugar consumption and T2D prevention.