That is because a soda habit increases the risk of developing a condition called metabolic syndrome, according to the new research, and that in turn boosts the chance of getting both heart disease and diabetes.

"Even one soda per day increases your risk of developing metabolic syndrome by about 50 percent," says Ramachandran Vasan, MD, professor of medicine at  Boston University School of Medicine and the senior author of the study, published in the July 31 issue of the American Heart Association's journal Circulation.

To be diagnosed with metabolic syndrome, three of five criteria must be met: a large waistline, elevated blood pressure, elevated fasting blood sugar, elevated fasting triglycerides, or reduced HDL or "good" cholesterol.