Sugar is not great for your body. And diet regardless of artificial sweetener will have adverse effects in large doses. Many artificial sweeteners are known to cause cancers in rats and mice whether this applies directly to humans is still unknown. I get headaches when i drink over 5 cans in one sitting, so there is just one side effect. I may have a potential hypothesis for this. I believe the body attempts to use the artificial sweetener as real sugar, this artificial sweetener acts as a competitive inhibitor in the glucose pathway to the brain causing headaches.
What do you fear more; potential obesity and diabetes or potential cancers?