A new survey of soda drinkers from Johns Hopkins turned up some potentially surprising evidence: Overweight people who choose to drink diet soda instead of regular don't consume fewer daily calories overall. Among people with normal-weight body mass indexes, however, diet soda consumption was linked to taking in fewer total calories throughout the day.

The study, published in the American Journal of Public Health, doesn't speculate as to why overweight and obese diet drinkers are affected differently. But one possible explanation is the "halo effect," which is known to plague dieters of all sizes. It works like this: Proud of virtuous efforts to cut calories in some aspect — by drinking diet soda, having a salad for lunch, skipping the office donuts in the a.m. — dieters then (consciously or unconsciously) make up the calories elsewhere throughout the day.

But there is a silver lining here: While diet soda drinkers consumed similar calories to regular-soda fans, more of these calories came from food than from beverages. Food calories at least have the potential to be more filling and more nutritious than the totally empty calories in a can of Coke or Sprite. There's a world of difference between the 150 calories in a 12-ounce can of regular soda and the 150-calories in a piece of whole-wheat toast with avocado (and a lot less sugar, too). So don't go swapping the diet back for regular soda just yet, folks.