The Og Fat Mystery; Using Abbreviations Sensibly
If the copy writer intended to mean “contains no trans fat”, then I would respectfully suggest writing exactly that: “contains no trans fat”. Reasonable alternatives might include “trans fat free” or “contains zero trans fat”. If you wanted to put a more positive spin you could try “contains only healthy fats” or something like that.
“0g” as an abbreviation for “nothing” is a very poor alternative. I understand that abbreviations have a useful role to play in communications, but there is no point in using “0G” when the word it replaces – “no” – is exactly the same length and much clearer. In addition, because it includes a number that can be mistaken as a letter it is doubly confusing. A pedant might also question the need for a unit at all when the value is zero -- there is, after all, no difference between zero grams and zero ounces -- but it does emphasis that the quantity is zero and this is acceptable in a non-scientific context.
There are some simple rules that careful writers apply when using abbreviations. First of all, never use an abbreviation when it is not really necessary -- which I believe is the case here. Second, never use an abbreviation containing an ambiguous mixture of letters and numbers such as 5/S, 1/I or 0/O. Finally, if you have to use an abbreviation then make sure that at least once it is spelled out in full unless it is one of those things that really everyone knows – and test this on a few people first to make sure.
To be fair there is also an "og" symbol, which is much more effective because of the way the human eye-brain system works. The reason is that the brain can match symbols seen on the box with previously stored images very quickly. But this does not excuse the use of og in the copy.