A recent European study found that consuming just ONE soda a day can increase your risk of developing type 2 diabetes by 22 percent! This study supports United States based research that has found the risk a little higher at up to 25 percent increased risk.
How can just one soda do all this? Well, the calories from soda offer you absolutely no nutritional value. They just sit there. Combined with inactivity, over time, the problems add up. You can read about the British study on ABC News here.
I would also note that diet sodas are no better. I have written an extensive article on the danger of diet soda, here.