Diet fizzy drinks are one of the small treats we can allow ourselves, even if we're trying to watch our waistlines.
So we're devastated to report that they could actually be making us put on MORE weight that the full fat versions.
It's all down to sweeteners like aspartame.
Boffins have conducted the physiological impact of these and, as from the authors of the San Antonio Heart study, it makes grim reading.
It's down to the substantial study of 5,158 participants, whose height, weight, and artificial sweetener drink consumption was measured.
Then, nine years on, the academics went back to them - well, the 3,682 who were left - and found that, of those who drank 21 or fewer drinks with artificial sweeteners every week versus those who drank none, the risk of being overweight or obese almost doubled - and they had a greater BMI than those who didn't drink them.
Sounds like 'diet' doesn't mean what we thought it meant...