nope afraid not . the theory being that coke zero makes you hungry and may bring your appetite back and will make the diet hard to stick to . I was a pepsi max addict when I started ( at least 2 litres a day ) .. and after 8 weeks on lT I had a small can on xmas day .. and it was horrible !!! tasted so acidic and now I stick to water even on planned 'cheats '
It's about you cleansing your palatte too, LT is about forgetting all the things you did like and not falling back into old bad habits.
I know some people who do allow themselves the odd one but it's on your head be it if you do have one and then it leads to hunger cravings on top. If you are at the beginning of LT i would strongly suggest you don't have it! HTH
Cambridge does not recommend the use of carbonated, so-called 'zero calorie' drinks. They are usually not 'zero calorie' an can lead to a feeling of bloating, as well as perpetuating the taste for other conventional foods.
My advice is don't do it. Its not just about carbs and calories its all about taste and perception too. One coke zero with no carbs may lead to one bit of cheese with no carbs to a piece of ham with no carbs and then it is very hard to get back on track whether you are in ketosis or not. Even if you have fantastic will power which we all must have to be doing LT. But trust me I had a slip up a few weeks ago and had coke zero followed by a bit of cheese and a bit of ham etc it was very very hard to get back on track and each day now is very hard and twice as hard as before.
I would strongly recommend sticking to just the LT stuff with no additions. It really does work. I wish I never had that sip of coke zero as it re-awakened my taste buds too soon I am now looking forward to my refeed and doing it properly!
It could also be down to the type of acid within the drinks. Coke Zero has phosphoric acid whereas most other diets drinks have citric acid and its the citric acid that could throw you of ketosis. This was explained to me on the Exante forum when someone there raised a similar question. So following that thought process Coke Zero could be drunk - but as mentioned above it will 'contaminate' your palate and make you think of food/drink - believe me - stick to your water and black tea/coffee - its so not worth breaking the LT diet just to have a different taste.