Some decades back I designed a family of measuring instruments for a company wanting to do alcohol breath testing.
The problem of distinguishing breath acetone from ethyl alcohol was a serious technical difficulty then and evidently still is. Reason is that the real-time sensors which are most practical and field-worthy for use in such devices tend to have difficulty distinguishing between these two quite similar organic molecules. More comprehensive tests - easy to obtain from instruments that spend their lives sitting on a table in a clean, temperature and environment controlled room - can readily make the distinction. Such is the zen of measurement.
Here is some general information about metabolism and Ketosis:
http://en.wikipedia.org/wiki/Ketosis
And here is a study showing the direct link between diet and acetone in the breath:
http://www.ajcn.org/cgi/content/full/76/1/65
Clearly there's a need for some education about the risk of confusing alcohol and acetone on the breath. Training needed for the security people and also for the distinguished members of the press who tend to go over the top on these reports.
If I, as a pilot and sometimes also a low-carbivore, were concerned about breath testing at security creating a false positive, a few ounces of sweet chocolate - fruit juice - raw sugar, etc. half an hour before the event would seem like a precautionary way to snuff ketosis and largely eliminate breath acetone .... but I am not a doctor and am not qualified to offer advice in this regard.