The irony of diet sodas is, even though they have zero calories, they actually are responsable for making you gain fat by fooling your brain chemistry.
Using MRI technology, researchers evaluated the brain responses of young adults who drank diet soda (saccharin sweetened) vs the ones who drank conventional soda (sugar sweetened). Their results showed that the reward-processing centers of the brain had much greater activation in the saccharin sweetened group.
Plus the diet soda drinkers had reduced caudate head activation (brain neuron stimulation responsable for emotions, memory and learning), thus indicating that “there are alterations in reward processing of sweet taste in individuals who regularly consume diet soda, and this is associated with the degree of consumption.”3
More simply, artificial sweeteners increase our desire for more fattening sugars, starches and carbohydrates such as doughnuts. If you drink diet soda, you’re more likely to consume extra sweets to calm your cravings. On top of that, artificial sweeteners fools your body chemistry into thinking more sugar is on the way, which leads to the production of greater insulin levels, increasing inflammation and visceral fat in the body.
Drinking that Diet Coke is not so appealing anymore ?
Green, E., Murphy, C.; Altered processing of sweet taste in the brain of diet soda drinkers, Physiol Behav. 2012 Nov 5;107(4):560-7. doi: 10.1016/j.physbeh.2012.05.006. Epub 2012 May 11