High fructose corn syrup, a common sweetener of beverages, reduces insulin sensitivity and may contribute to heart disease. The type of high fructose corn syrup used in soft drinks consists of 55% fructose and 45% glucose… a ratio similar to table sugar.
Drinking a fructose sweetened drink at each meal increased fasting glucose levels and decreased the glucose and insulin responses associated with the meals, indicating impaired signaling. Triglycerides and fasting apolipoprotein-B, both heart disease risk factors, were also significantly increased.
Fructose does not directly increase blood sugar levels, but contributes to insulin resistance through its impact on liver function and triglyceride levels. The amount of fructose in fruit is not enough to induce insulin resistance. In fact, fruit improves insulin resistance because of polyphenol activity and fiber.