Residents of Kansas who are on the popular keto diet for health and weight loss might want to hear about a curious drunk driving case that happened earlier this year. The Houston-area attorney for a man who was charged with DUI got the charges dropped after discovering that his client was on the keto diet. The attorney claims that a positive breath test was reading alcohol on the man’s breath that was not there because he had been drinking, but because he was in ketosis.

The keto diet is a low-carbohydrate, high-fat diet that puts the body in a metabolic state called ketosis. In ketosis, the body becomes more efficient at burning fat. But ketosis also creates acetone in the body, which can be released through the breath as isopropyl alcohol.

The type of alcohol people drink – ethanol alcohol – differs from isopropyl alcohol, but a breath test for alcohol impairment might not be able to tell the difference. Experts say it could depend on the type of breath test device used. A researcher who did a study on the subject in 2006 says he has never seen evidence that alcohol breath testing can distinguish between the two types of alcohol. But one manufacturer says his company’s device is designed to do just that.

If someone has been drinking and happens to be on the keto diet, testing could become even more complicated. But in most states, roadside breath test results are not used in court. Further testing is often done to determine if there is enough evidence of impairment for charges to be made.

As opposed to a breath test, a blood test that measures the amount of alcohol in the blood might seem to be undeniably scientifically accurate, but that is not necessarily the case. Someone who has been charged with drunk driving could challenge the results of a blood test and possibly get the charges reduced or even dropped.