Which are worse: sugary drinks or diet drinks?

Geneticist and metabolism expert Giles Yeo answered this question...

Giles - This is a hot topic at the moment. Let's just deal with one thing out there: a lot of people says that artificial sweeteners, aspartame, Stevia, whatever... I mean, the first thing is, look, people say that sweeteners are cancerous. They're cancerous if you stuff a hundred litres of a diet soda into a rat. That will cause cancer. But at the levels and at the doses that we actually drink it, like in a can or anything like that, they're not cancerous. So that's the first thing that we need to worry about. But - and this is the big but here - is there something that happens where if you drink a lot of diet soda, you actually break the communication between the taste and the amount of nutrients you're actually absorbing? Because ultimately we evolve through that, "ooh, a red berry, ooh, sweets, ooh, calories". So this is sort of the way that our primitive brains work.

But if you actually break that connection - so in other words you have the sweet flavour, you drink it, but you then absorb no nutrients - the longer term question is, will it then end up affecting your metabolism in some way, subtly or otherwise, and therefore increasing your risk of disease? Now here, I can't give you a straight answer. I think there is some evidence that this does happen, that this disconnect between the flavour and the number of calories, the amount of nutrients you actually eventually absorb, will actually begin in the long term to start messing about with your metabolism. Now, does this mean it is worse for you than the full sugar drink? Now it depends who you are. Now clearly, if you're a diabetic, then it is not. Please don't be drinking the full sugar drink. If you suffer from obesity, maybe you should be considering not drinking the full sugar drink. And if you are a kid, a child, particularly a young child, I think we need to have children drinking less sugar. So my answer is going to be that a diet beverage, a diet drink is going to be not as bad as a full sugar drink for many people, but ultimately water is the best drink that you can drink.