Kelly Brownell, a renowned obesity expert, is one of many who confirm that science shows us that the calories in beverages don't fill us up in the same manner in which food does. Hence, you can sip continuously throughout your day and your brain doesn't register that your tank is full. It is often most prudent for most of us to eat our calories instead of drink our calories for this very reason.
Obesity experts will also tell you that obesity is much more complex than calories alone, yet, consciously or unconsciously managing calories is often necessary to achieve weight loss. Frustrating as it is, you have to eat or drink the right size in order to wear "the right size" - another "food that fits" philosophy in which food and fashion tango!
I'll drink (water) to that!