The consumption of sugar-sweetened beverages has been associated with weight gain. These beverages include soft drinks, fruit drinks, iced tea, energy drinks and vitamin water.
These types of drinks have also now been associated with metabolic syndrome and type 2 diabetes (Malik VS, et al. 2010). Metabolic syndrome is a condition which includes insulin resistance, elevated cholesterol, triglycerides and elevated blood pressure.
When data from studies including 310,819 participants and 15,043 cases of type 2 diabetes was analyzed it was found that individuals in the highest quantile intake of these beverages (most often 1-2 servings per day) had a 26% greater risk of developing type 2 diabetes than those on the lowest quantile (none or less than 1 serving per month).
Just from eliminating these types of drinks you have a better chance of preventing both weight gain and serious diseases.